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MAINTENANCE (Heb. מְזוֹנוֹת, mezonot), generally speaking, the supply of all the necessaries of the party entitled thereto, i.e., not only food, but also matters such as medical expenses, raiment, lodging, etc. (Sh. Ar., eh 73:7; see *Husband and Wife). When, however, the maintenance obligation is based on a personal undertaking (see below) and not on the operation of law, it will not cover raiment and perhaps not even medical expenses, unless the contrary is indicated by the terms of the undertaking (Sh. Ar., eh 114:12; Rema, Ḥm 60:3; Siftei Kohen thereto n. 14). The liability of maintenance exists generally by virtue of law, but in the absence of any legal duty it may also be based on a voluntary undertaking (e.g., by the husband toward his wife's daughter by a previous marriage). Even though it is normally for an unfixed amount, such an undertaking will be binding and be governed by the general law of obligations (Sh. Ar., Ḥm 60:2, contrary to the opinion of Yad, Meḥirah 11:6; see also *Contract; *Obligations, Law of).

The liability of maintenance by virtue of law is imposed on (1) a husband toward his wife; (2) a father toward his small children; and (3) the heirs of the deceased toward his widow. A divorced wife is not entitled to maintenance from her former husband (Sh. Ar., eh 82:6; see *Divorce), nor, generally speaking, a betrothed woman from the bridegroom (Sh. Ar., eh 55:4 and Rema thereto). Only maintenance between husband and wife, as a liability by virtue of law, will be discussed below (see also *Widow; *Parent and Child).

Scope of the Maintenance Obligation

The husband's duty to maintain his wife is one of the duties imposed on him by virtue of his marriage as obligatio ex lege (Yad, Ishut 12:2; Sh. Ar., eh 69:2). He has to provide her with at least the minimal needs for her sustenance in accordance with local custom and social standards (Yad, Ishut 12:10; Sh. Ar., eh 70:3). In addition and subject to the aforesaid, the wife's right to maintenance is governed by the rule that she "goes up with him but does not go down with him" (Ket. 61a; Tur, eh 70), i.e., the wife, regardless of the standard of living she enjoyed prior to the marriage, is entitled to a standard of living which matches that of her husband and to be maintained in accordance with his means and social standing. At the same time, she is not obliged to suffer having her standard of living reduced to one below that which she enjoyed prior to her marriage, at any rate not as compared with the standard of living customary in her paternal home with regard to family members backed by means similar to those available to her husband, even if he should choose a lower standard of living than he can afford (Yad, Ishut 12:11; Sh. Ar., eh 70:1, 3 and Ḥelkat Meḥokek thereto n. 1). In addition to providing for all the domestic needs of the common household and as part of his duty of maintenance in its wider sense, the husband must give his wife a weekly cash amount for her personal expenses, again in accordance with their standard of living and social custom (Sh. Ar., eh 70:3; Ḥelkat Meḥokek thereto n. 7). In return for this obligation, the husband is entitled to his wife's "surplus handiwork," i.e., to her earnings from work done beyond the call of her legal duty toward him (Ma'aseh Yadeha). The said obligation being imposed on the husband as part of his duty to maintain his wife, she may, of her own choice, waive her right to the weekly allowance in order to retain for herself such surplus earnings, just as she may waive her maintenance in order to acquire for herself the proceeds of her handiwork (Ḥelkat Meḥokek loc. cit.). The unspent balance of the money given the wife for her maintenance belongs to her husband, since he is only required to give her an amount sufficient for her needs (Ket. 65b; Yad, Ishut 12:13; Pitḥei Teshuvah, eh 70 n. 1). However, if such balance results from the wife's spending less than she requires for her own needs, it belongs to herself; she need not invest the amount of it and if she should do so, the fruits of such investment would belong to her alone (see *Dowry). Another opinion is that money given by the husband for his wife's maintenance always remains his own, except insofar as she actually expends it on the household or on her own maintenance, and therefore any balance, even if saved, belongs to him (see Rema, eh 70:3; Pitḥei Teshuvah, eh 70 n. 1; pdr 2:229 and 289).

The wife's right to be maintained in the manner described above is independent of the fact that she may be able to maintain herself out of her own property and the fact that her husband may be in financial difficulties. She will accordingly not be obliged to sell her property or to use fruits thereof, to which her husband has no right, in order to facilitate his fulfillment of his obligation to maintain her, since he has undertaken the obligation on the marriage and it is also expressed in the ketubbah deed in the phrase, "I shall work and support you" (see below, Sh. Ar., loc. cit. Pitḥei Teshuvah, eh 70 n. 2; pdr 1:97, 101f.).

Separated Parties

In general, the husband is only obliged to maintain his wife as long as she lives with him or, at any rate, if he is not responsible for the fact that they are separated (Rema, eh 70:12). Hence in the case of separation of the parties, it is necessary to establish which of them has left the common home.

when the husband leaves the home

In principle the wife's right is not affected: "She was given to live and not to suffer pain" (Ket. 61a) and the husband remains responsible for her maintenance (Mordekhai, Ket. no. 273). To frustrate her claim, the husband must prove a lawful reason for his absence and refusal to maintain her, e.g., her responsibility for a quarrel justifying his departure (Rema, eh 70:12). However, even in circumstances where the husband is responsible for maintaining his wife despite their separation, it will nevertheless be presumed that he has left her with sufficient means to support herself for a reasonable period during his absence and therefore, in general, she will not be awarded maintenance during the first three months following his departure (Ket. 107a; Sh. Ar., eh 70:5). For the wife to succeed in a claim brought within this period, she must prove that her husband has left her without any means at all, or will have to rebut the above assumption in some other manner, e.g., by proving that her husband left the home as a result of a quarrel or with the intention of returning after a short interval but for some reason failed to do so (Rema, eh 70:12; Beit Shemu'el 70 n. 11; Ḥut ha-Meshullash, 1:6, 4).

The husband is not entitled to demand that his wife should work and support herself out of her earnings during his absence unless she has expressly or by implication consented to do this (Yad, Ishut 12:20; Maggid Mishneh thereto; Sh. Ar., eh 70:9; Ḥelkat Meḥokek 70 n. 33). This is so regardless of whether or not she has been accustomed to working prior to his departure and handing over her earnings to her husband, according to law. The court will not of its own initiative investigate the matter of the wife's earnings from her own handiwork, but will take this into account only if it emerges out of the wife's own arguments. However, if after his return the husband can prove that the wife has been working and earning during his absence, he will not be obliged to repay a loan his wife has taken for her maintenance (see below), to the extent that he proves that she was able to support herself from such earnings during his absence. In this event he will similarly be entitled to demand that she refund to him all amounts she has recovered out of his property for the purposes of her maintenance (Yad, Ishut 12:16; Sh. Ar., eh 70:5).

When the wife is entitled to maintenance but her husband leaves her without sufficient means and she does not maintain herself out of her own earnings, she has the right to borrow for her maintenance and to hold her husband liable for the repayment of such a loan (Ket. 107b; Yad, Ishut 12:19; Sh. Ar., eh 70:8). This is not the case if prior to his departure she was supporting herself by her own efforts and remained silent when he publicly disavowed responsibility for debts she might contract, thus seeming to have consented to this (Rema, eh 70:12; Beit Shemu'el 70 n. 32). The husband's duty to repay such a loan is toward his wife only and he is not directly liable to the creditor. If, however, the wife has no property of her own, or if for any other reason the creditor might have difficulty in recovering from the wife, he may claim repayment of the loan from the husband directly, in terms of the *Shi'buda de-Rabbi Nathan (permitting the creditor to recover the debt directly from a third party who owes money to the principal debtor if the creditor has no other means of recovering from the latter (Yad, Ishut 12:19; Rema, eh 70:8)).

If the wife has sold some of her own property to support herself, she will be entitled to recover from her husband the equivalent of the amount realized, provided that the facts do not demonstrate any waiver of this right on her part, such as an express declaration to this effect made by her before witnesses at the time of the sale, or if at that time there was a suit for divorce pending between the parties. If proof to this effect is forthcoming, the wife will not be entitled to recover anything from her husband since it is presumed that as long as the marriage tie is in existence, she will not do anything which might bring about its complete severance and will therefore also be prepared to waive her pecuniary rights against her husband (Rema, eh 70:8; Beit Shemu'el 70 n. 29; pdr 2:289, 291f.). Whenever the wife is not entitled to a refund of the amounts she has expended, during the period of her husband's absence, the earnings from her handiwork will be loans to her (Rema, eh 70:8).

Third parties who of their own accord assist the wife in respect of her maintenance are not entitled to be refunded for their expenditure – neither from the wife since she has not borrowed from them, nor from her husband since he has not instructed them to do so – but they are in the position of one who "has put his money on the horns of a deer" (Rema, eh 70:8; see also *Unjust Enrichment). If the wife can prove that the assistance was given her in the form of a loan, the question of repayment will be governed by the aforesaid ordinary rules concerning a loan for purposes of the wife's maintenance, even if the assistance was given by her own parents (Mordekhai, Ket. no. 273).

when the wife leaves the home

In principle the husband is not obliged to maintain his wife unless she lives with him (see above). Hence the mere fact of her leaving him, or her refusal to return to him after she has left him lawfully, provides the husband with a prima facie defense against her claim for maintenance, since by living apart from him she precludes herself from carrying out her marital duties, on due fulfillment of which her right to maintenance is dependent. Therefore, to succeed in a claim for maintenance in these circumstances, the wife must discharge the onus of proving facts justifying her absence from the marital home (Rema, eh 70:12; Beit Shemu'el 70 n. 34; pdr 6:33, 52f.). These may arise either from the husband's bad conduct toward her – e.g., his responsibility for a quarrel justifying in law her refusal to continue living with him together in the marital home (Beit Yosef, eh 70, end; Sh. Ar., eh 70:12) – or from other circumstances which are independent of the husband's blameworthy conduct toward her, such as his refusal to comply with her justified demand to move to another dwelling or to live away from her husband's relatives who cause her distress (see *Husband and Wife). In general it may be said that any reason sufficient to oblige the husband to grant his wife a divorce will entitle her to claim maintenance from him even though she may have left the home, since the fact that the husband is obliged to grant her a divorce means that he must acquiesce in their living apart; therefore her refusal to live with him entails no breach of her duties toward him. Moreover, by unlawfully withholding a divorce from his wife the husband prevents her from marrying someone else who could maintain her, and there is a rule that a husband who, contrary to law, prevents his wife from marrying another man renders himself liable to maintain her until he grants her a divorce (pdr 1:74, 77–80). If the wife leaves the home on account of a quarrel she has unjustifiably caused, and generally when she has no justifiable reason for living apart from her husband, she will not be entitled to maintenance from him.

For other cases in which the wife forfeits her right to maintenance, see *Husband and Wife (s.v.moredet); *Divorce.

Claim for Maintenance Cannot Be Assigned or Set Off

The husband is not entitled to set off against her claim for maintenance any pecuniary claim he may have against his wife, such as one arising from her sale, contrary to law, of her husband's property for purposes of her maintenance during his absence. His duty to maintain his wife means to provide her with the necessities of life with him, i.e., entails responsibility for her daily needs with regard to food, raiment, lodging, etc. This affords the wife a right against which pecuniary debts cannot be set off, since those two differ in their legal nature and her daily needs cannot be satisfied by a reduction of the debt she owes him (pdr 1:333, 338; 2:97, 99). If, however, the wife's claim is based on a right whose legal nature is purely pecuniary, e.g., her claim for repayment of a loan she has taken for her maintenance, there will be no bar to the husband setting off against such claim any other pecuniary claim he may have against her, if, for instance, she is indebted to him for a loan she obtained from him for the purpose of supporting her relatives – he may also set off such pecuniary claim against her claim with regard to payment of her ketubbah at the time of their divorce (see pdr 1 loc. cit.). The same reason that entitles the wife to receive actual payment of her maintenance prevents her from assigning this right to others (Beit Shemu'el 93 n. 18).

Arrear Maintenance

If the wife, although entitled to maintenance, does not bring an action for it in the court, she will be unable to claim maintenance for any period preceding the date of bringing her suit, since it will be presumed that she preferred to suffer rather than unfold her troubles before the court and her silence will therefore be interpreted as a waiver of her right for such a period (Yad, Ishut 12:22; Sh. Ar., eh 70:11). This presumption may be rebutted by evidence showing that she insisted on her rights, e.g., that she demanded her maintenance from her husband and refrained from instituting action only because of his promise to comply without recourse to the court (Rema, eh 80:18; Beit Shemu'el 80 n. 27); institution of action has the same effect for any period thereafter even if a considerable amount of time elapses before judgment is given (Rema 70:5; Beit Shemu'el 70 n. 12; see also *Limitation of Actions).

Non-payment of Maintenance: Consequences

On the husband's failure to maintain his wife in the manner to which she is entitled, the court – at her instance – will order him to do so, whether he refuses payment although he has the means to meet it or whether he lacks the means because he does not work although he is able to work and earn this amount. In other words, the husband will be ordered to pay maintenance in accordance with his potential working and earning abilities, and not necessarily his actual earnings, for he has undertaken in the ketubbah to work and to maintain his wife (Rema, eh 70:3; Ḥelkat Meḥokek 70 n. 12). If he has sufficient for his own needs only for a single day, he must still share this with his wife since he is liable to maintain her "with himself" (Rema, eh 70:3). On the other hand, as he has to maintain her "with him" only, i.e., to no greater extent than he is able in respect of himself, he will be exempt from maintaining her if he cannot afford it because he is in a position of utter poverty and unable to work and earn for reasons beyond his control (Pitḥei Teshuvah, eh 70 n. 2; Perishah, Ḥm 97 n. 41). For the same reason, inability to pay maintenance is excused on grounds of the husband's need to repay regular debts, these taking preference over the former (ibid.). If the wife should not wish to content herself with a claim for maintenance, she may possibly be entitled to demand a divorce.

In the State of Israel

Maintenance for the wife is a matter of personal status within the meaning of article 51 of the Palestine Order in Council, 1922, and is therefore governed by Jewish law (sec. 51 thereof) even when claimed in a civil court by virtue of section 4, Rabbinical Courts Jurisdiction (Marriage and Divorce) Law, 5713 – 1953. So far as a Jewish wife is concerned, the above position was left unchanged by the Family Law Amendment Maintenance Law, 5719 – 1959, which expressly provides that the question of her maintenance shall be governed solely by Jewish law (sec. 2; see Supr. pd 15 (1961), 1056, 1058). If the husband refuses to comply with a judgment of the court for the payment of maintenance, he may be imprisoned for a period not exceeding 21 days for every unpaid installment (Executive Law 5727 – 1967, sec. 70ff.); see also Imprisonment for *Debt.

[Ben-Zion (Benno) Schereschewsky]

Maintenance (Mezonot) in the State of Israel

Maintenance payments in Israel are determined in accordance with Jewish law, as stipulated in Section 2 of the Family Law (Maintenance) Amendment Law, 5719 – 1959. In this respect, the position described above remained unchanged. This update will deal with a number of issues in which new arrangements were established in Israeli law, in both the rabbinical courts and the general courts.

maintenance under the law of meukevet meḤamato (a woman prevented from remarrying owing to her husband's refusal to give her a get)

In Jewish law – and in Israeli law, too, which applies Jewish law – the husband's obligation to pay maintenance derives from the fact of the marriage and the husband's undertaking in the ketubbah to provide for his wife – an obligation that terminates upon divorce. Accordingly, where the husband is obligated to grant a divorce – and refuses – the question arises as to how this refusal affects his maintenance obligation. Under Jewish law, even if the couple do not live together, the husband remains liable for maintenance, because his refusal to grant his wife a get prevents her from marrying someone else, thereby denying her maintenance from a potential husband. Furthermore, in such circumstances a different set of rules applies. By law, the husband owns the wife's handiwork (ma'aseh yadeha) – the fruits of his wife's labor – and practically, such fruits (e.g., income) are deducted from her maintenance. But when the maintenance obligation is imposed by reason of the husband's refusal to give a get, the latter is not entitled to deduct her income. The explanation is that the husband's ownership of his wife's handiwork against his obligation to support his wife derives from the consideration of ill-feeling (eivah). In other words – it was instituted in the interests of domestic peace (shelom bayit) between the spouses (see *Husband and Wife). However, when the husband refuses to grant a get to the wife, there is no justification for entitling him to her earnings, because there is no longer an interest in fostering domestic harmony, but rather in terminating the marriage with a get. The Israeli Supreme Court thus ruled that a maintenance award based on the wife's inability to marry because of her husband is only applicable after the rabbinical court has ruled on divorce, in one of the following manners: forcing or obligating the husband to grant a get, as well as the more "moderate" case in which the court orders the parties to divorce. This principle was established by the Rabbinical Court of Appeals (dayyanim A. Goldschmidt, S. Yisraeli, J. Kapah; Appeal 205/5733, pdr 10, 294), and was adopted in a ruling of the Supreme Court (comments of President, M. Shamgar, ca 792/82, Nuni v. Nuni, 40 (3) pd 744, following Justice M. Elon, hc 644/79 Gutman v. the Rabbinical Court, 34 (1) pd 443, and the comments of Judge Y. Cahn in hc 661/77 Haber v. the Rabbinical Court, 32 (3) pd 324).


In 1975, a chapter dealing with maintenance was added to the Civil Procedure Regulations – Chapter 23 (3) of the Civil Procedure Regulations, 5723 – 1963. Its central innovation was the requirement that every statement of claim or defense dealing with maintenance be supported by an affidavit. In addition, a detailed specification had to be submitted as an appendix to any claim or defense, detailing the complete assets and income of each party (including documentation, such as wage slips for an entire year), as well as the sums that, in that party's opinion, would meet the maintenance needs of the (rival) parties. Under these regulations, the District Court (which had jurisdiction over maintenance cases at that time) conducted an initial enquiry based on the material submitted, fixing temporary maintenance accordingly, without having to conduct a separate proceeding. These regulations also established sanctions for failure to comply with the regulations, by not attaching substantiating documentation, concealing particulars, or otherwise contravening the regulations. The sanctions ranged from orders to comply with the regulations, to the possibility of accepting the other party's claims (see, e.g., the ruling of the Jerusalem District Court, am 470/03 Anon. v. Anon.; am 789/05 ad v. ay).

The Civil Procedure Regulations 5744 – 1984 incorporated the same maintenance provisions in Chapter 21 (Regulations 259–266). In 1995 the Family Courts Law (see Family Courts Law, 5755 – 1995) was adopted and the powers of civil instances to adjudicate maintenance cases were transferred to the Family Court. Maintenance suits are now governed by the civil procedure regulations applying to all claims adjudicated in the Family Courts (Part 3.1 of the Civil Procedure Regulations, 5744 – 1984; Regulation 258A –258gg).

Apparently, the enactment of procedure related regulations in the general court system, including with respect to the Family Court, led to the enactment of the new regulations governing rabbinical courts procedure (1993). Regulation 33 of these regulations determined that a maintenance claim must be submitted together with the form indicated in Regulation 211, and the defendant is instructed to follow suit when submitting his statement of defense. Pursuant to Regulation 211, special forms were prepared for maintenance claims in the rabbinical courts, in which, as part of the specification of data, the husband is required to declare the sums of maintenance paid prior to submission of the claim together with particulars of his income and property. A number of rulings have determined that failure to attach the specification of data form, or to properly complete it, may be taken into account when assessing the sincerity of the "inclusion" of a maintenance claim in a divorce suit in the rabbinical courts (see ff (Tel Aviv) 16981/96 Dahan v. Dahan; on the inclusion of maintenance with a divorce case, see *Bet DinRabbani – Rabbinical Court in Israel).

enforcement of maintenance payment

The State of Israel enforced court maintenance awards by means of the Execution Office, pursuant to the provisions of the Execution Law, 5727 – 1967. This mechanism likewise enforces maintenance awards of rabbinical courts (see under *Rabbinical Court; *Execution, Civil).

Maintenance differs, in principle, from any other monetary ruling. In a regular civil file, the court is only required to consider the question of whether the defendant is liable or not; the defendant's financial capacity to pay the sum of the claim does not affect his liability. On the other hand, liability for maintenance, in principle, is based on the financial capacity and situation of the liable party, and the sum of maintenance is fixed in accordance with a number of parameters, inter alia, the liable parties' financial ability to pay a particular sum of monthly maintenance (after he has borne his own expenses). This distinction affects the discretion exercised by the head of the Execution Office in determining how a debt is paid. Regarding a regular debt, the head of the Execution Office may, and is often compelled to, consider the debtor's financial situation, in view of which he determines whether he should pay the debt in one payment or in installments. Regarding a maintenance ruling, the head of the Execution Office does not have such discretion and must implement the court's ruling literally, inasmuch as the judicial forum that ruled on maintenance (a rabbinical court or the family court) has already considered this data and the sum of the maintenance ruling was determined on the basis of that data.

Another difference between collection of a financial debt as distinct from a maintenance debt relates to the use of imprisonment. The Execution Law and Supreme Court rulings restricted the cases in which imprisonment can be imposed against a person who fails to discharge his civil debt (see the detailed ruling of Deputy President Judge M. Elon in hc 5304/92, Perach v. the Minister of Justice, 47 (4) pd 715; see in detail: *Execution, Civil). In contrast, Section 74 of the Execution Law determines that regarding a maintenance debt, the head of the Execution Office may, at the request of the person entitled to maintenance, issue an arrest warrant against the debtor, even without investigating his financial ability (one of the minimal terms required for imprisonment with respect to a civil debt). The Supreme Court emphasized the difference between collection of a maintenance debt and collection of a regular civil debt: the maintenance award is fixed by a judicial instance [after having consideration for the liable party's financial situation]; the dependency of the persons entitled to the maintenance on the maintenance payments for their sustenance; the fact that a maintenance ruling is not final and the debtor may apply to a rabbinical court or the family court to alter the amount of the maintenance if there has been a change of circumstances justifying its alteration (p. 731 of the Perach decision).

In addition, a special social welfare law was enacted in Israel enabling receipt of maintenance payments through the National Insurance Institute (The Maintenance (Assurance of Payment) Law, 5732 – 1972). According to this law, a person with a maintenance ruling in his favor (such as a spouse or child) may present a copy of the judgment to the National Insurance Institute and the latter will pay the maintenance sum on a monthly basis (subject to a statutory ceiling; see Section 4 of the law). The National Insurance Institute acts on behalf of the person entitled to maintenance, and concurrently initiates execution proceedings against the maintenance debtor.

In this way, those entitled to maintenance receive the monthly payment with dignity and without tension or pressure in the event of the maintenance debtor's failure to pay. This law is particularly effective when the maintenance debtor changes addresses and cannot be traced or absconds abroad. The difference between the sum awarded as maintenance by the Court (either Rabbinical or Family Court) and the sum actually paid by the National Insurance Institute, may be collected by the entitled party by opening a file in the Execution Office (see Section 10 of the law; am 789/05 ad v. ay).

[Moshe Drori (2nd ed.)]


Gulak, Yesodei, 1 (1922), 37; 2 (1922), 68–70; 3 (1922), 37–39; Gulak, Oẓar, 149–58; et, 1 (19513), 324f.; 4 (1952), 80–83, 91f.; 6 (1954), 656; Regional Rabbinical Court, Tel Aviv, Judgment, in: Ha-Torah ve-ha-Medinah, 9–10 (1957/59), 185–99; B. Cohen, in: paajr, 20 (1951), 135–234; republished in his: Jewish and Roman Law, 1 (1966), 179–278; addenda: ibid., 2 (1966), 775–7; B. Schereschewsky, Dinei Mishpaḥah (19934), 106–33; Elon, Mafte'aḥ, 122f.; idem, Ḥakikah Datit… (1968), 44–46, 60–62; H. Baker, Legal System of Israel (1968), index. add. bibliography: M. Elon, Ha-Mishpat ha-Ivri (1998), 1:111, 129, 188, 468f., 518, 638, 653; 3:1337, 1392f., 1417, 1476, 1479, 1499f., 1596; idem, Jewish Law (1994), 1:125, 145, 211; 2:571f., 631, 791, 808; 3:1597; 4:1660f., 1687, 1756, 1760, 1784f., 1904; M. Drori, "Sidrei Din Ḥadashim bi-Teviot le-Mezonot," in: Ha-Praklit, 31 (1977), 317–40.

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Maintenance is the combination of all technical and associated administrative actions intended to retain an item in, or restore it to, a state in which it can perform its required function. Many companies seek to gain competitive advantage with respect to cost, quality, service, and on-time deliveries. The effect of maintenance on these variables has prompted increased attention to the maintenance area as an integral part of productivity improvement. Maintenance is rapidly evolving into a major contributor to the performance and profitability of manufacturing systems. In fact, some see maintenance as the last frontier for manufacturing.

In their article Make Maintenance Meaningful, P.K. Kauppi and Paavo Ylinen describe the bulk of maintenance procedures as being:

  • Preventive maintenancethe prevention of equipment breakdowns before they happen. This includes inspections, adjustments, regular service, and planned shutdowns.
  • Repair workrepairing equipment and troubleshooting malfunctions in an effort to return the equipment to its previous condition. These repairs may be reactive or preventive.
  • Improvement worksearching for better materials and improved designs to facilitate equipment reliability. Repair work is often a part of improvement work.

As shown in Figure 1, six maintenance programs are identified within the maintenance hierarchy, each representing an increased level of sophistication.


Reactive maintenance (also known as corrective maintenance) involves all unscheduled actions performed as a result of system or product failure. Basically, it is an attempt to restore the system/product to a specified condition. The spectrum of activities within this level is (1) failure identification, (2) localization and isolation, (3) disassembly, (4) item removal and replacement or repair in place, (5) reassembly, and (6) checkout and condition verification.

This approach is mainly a response to machine breakdowns. Unfortunately, many manufacturers are still in a reactive mode of operation, since their main objective is to ship the product. If their manufacturing equipment breaks down, they fix it as quickly as possible and then run it until it breaks down againan extremely unreliable process and not the best way to maximize the useful life span of assets. It leaves machine tools in a state of poor repair and can cause the production of out-of-tolerance parts and scrap. Because of its unpredictable nature it can easily cause disruptions to the production process.


Scheduled maintenance utilizes a previously developed maintenance schedule for each machine tool. While this is a broadly practiced technique in many manufacturing organizations, it does possess some distinct disadvantages. The scheduled maintenance may take place too soon, while the machine still operates well (1520 percent of all components fail after a predictable time), or it may come too late if the machine fails before the scheduled maintenance time. In some cases, the machine may still be running but producing unacceptable parts. Scheduled maintenance can be considered a part of preventive maintenance (discussed later) known as fixed-time maintenance (FTM).


Predictive maintenance involves performing maintenance on a machine in advance of the time a failure would occur if the maintenance were not performed. This means that one must calculate when a machine is predicted to fail. In order to do this, the firm must collect data on variables that can be used to indicate an impending failure (vibration, temperature, sound, color, etc.). This data is analyzed to approximate when a failure will occur and maintenance is then scheduled to take place prior to this time. By seeking the correct level of maintenance required, unplanned down-time is minimized.


Preventive maintenance encompasses activities, including adjustments, replacement, and basic cleanliness, that forestall machine breakdowns. Preventive activities are primarily condition based. The condition of a component, measured when the equipment is operating, governs planned/scheduled maintenance.

Typical preventive maintenance activities include periodic inspections, condition monitoring, critical item replacements, and calibrations. In order to accomplish this, blocks of time are incorporated into the operations schedule. The purpose of preventive maintenance is to ensure that production quality is maintained and that delivery schedules are met. In addition, a machine that is well cared for will last longer and cause fewer problems.

Current trends in management philosophy such as just-in-time (JIT) and total quality management (TQM) incorporate preventive maintenance as key factors in their success. JIT requires high machine availability, which in turn requires preventive maintenance. Also, TQM requires equipment that is well maintained in order to meet required process capability.

Preventive maintenance is also seen as a measure of management excellence. It requires a long-term commitment, constant monitoring of new technology, a constant assessment of the financial and organizational tradeoffs in contracting out versus in-house maintenance, and an awareness of the impact of the regulatory and legal environment.

The resulting benefits of preventive maintenance are many. Some of them are listed below:

  • Safety. Machinery that is not well maintained can become a safety hazard. Preventive maintenance increases the margin of safety by keeping equipment in top running condition.
  • Lower cost. A modern and cost-effective approach to preventive maintenance shows that there is no maintenance cost optimum. However, maintenance costs will decrease as the costs for production losses decreases. No preventive maintenance action is performed unless it is less costly than the resulting failure.
  • Reduction in failures and breakdowns. Preventive maintenance aims to reduce or eliminate unplanned downtime, thereby increasing machine efficiency. Downtime is also reduced when the preventive maintenance process gives maintenance personnel sufficient warning so repairs can be scheduled during normal outages.
  • Extension of equipment life. Equipment that is cared for will last longer than equipment that is abused and neglected.
  • Improved trade-in/resale value of equipment. If the equipment is to be sold or traded in, a preventive maintenance program will help keep the machine in the best possible condition, thereby maximizing its used value.
  • Increased equipment reliability. By performing preventive maintenance on equipment, a firm begins to build reliability into the equipment by removing routine and avoidable breakdowns.
  • Increased plant productivity. Productivity is enhanced by the decrease in unexpected machine breakdown. Also, forecast shutdown time can allow the firm to utilize alternate routings and scheduling alternatives that will minimize the negative effect of downtime.
  • Fewer surprises. Preventive maintenance enables users to avoid the unexpected. Preventive maintenance does not guarantee elimination of all unexpected downtime, but empirically it has proven to eliminate most downtime caused by mechanical failure.
  • Reduced cycle time. If process equipment is incapable of running the product, then the time it takes to move the product through the factory will suffer. Taninecz found, from an Industry Week survey, that there is a strong correlation between preventive maintenance and cycle-time reductions as well as near-perfect on-time delivery rates. Also, approximately 35 percent of the surveyed plants who widely adopted preventive maintenance achieved on-time delivery rates of 98 percent, compared to only 19.5 percent for non-adopters.
  • Increased service level for the customer and reduction in the number of defective parts. These have a positive direct effect on stockouts, backlog, and delivery time to the customer.
  • Reduced overall maintenance. By not allowing machinery to fall into a state of disrepair, overall maintenance requirements are greatly decreased.


Total productive maintenance (TPM) is preventive maintenance plus continuing efforts to adapt, modify, and refine equipment to increase flexibility, reduce material handling, and promote continuous flows. It is operator-oriented maintenance with the involvement of all qualified employees in all maintenance activities.

TPM has been described as preventive maintenance with these three factors added: (1) involving machine operators in preliminary maintenance activities by encouraging them to keep machines clean and well lubricated; (2) encouraging operators to report indications of incipient distress to the maintenance department; and (3) establishing a maintenance education and training program.

Developed in Japan, TPM places a high value on teamwork, consensus building, and continuous improvement. It is a partnership approach among organizational functions, especially production and maintenance. TPM means total employee involvement, total equipment effectiveness, and a total maintenance delivery system. In order to achieve this, machine operators must share the preventive maintenance efforts, assist mechanics with repairs when equipment is down, and work on equipment and process improvements within team activities.

Tennessee Eastman found that another employee, such as an equipment operator, with minimal training, could do 40 percent of the traditional maintenance mechanic's work. Another 40 percent could be performed with additional training, but still below the certified level. Only 20 percent of the maintenance tasks actually required a certified mechanic's skills. They also reported that as much as 75 percent of maintenance problems can be prevented by operators at an early stage. This frees maintenance personnel to be responsible for the tasks that require their critical skills, such as breakdown analysis, overhaul, corrective maintenance, and root cause analysis. This places maintenance personnel in a consultant role with the operators allowing them to:

  • Help the operator diagnose problems and restore equipment to like-new condition.
  • Use appropriate technologies and standards to verify that the equipment is in like-new condition after repair, overhaul, or replacement.
  • Use this knowledge to assess the root cause of the problem so that changes may be made to the design, operation, or maintenance practices in the future.
  • Work with purchasing, engineering, operations, and maintenance to modify procurement standards to assure maximum reliability in future equipment.

In order for this to work, the firm must have an organizational culture which supports a high level of employee involvement. Businesses must be willing to provide the necessary training in order to allow production personnel to perform the required tasks.

TPM's focus is on elimination of the major losses or inefficiencies incurred in production activities. These

losses include those due to obstruction of equipment efficiency, manpower efficiency, and material and energy efficiency. Based on their link to corporate goals, targets for eliminating or reducing these losses are developed.

Just as in activity-based cost accounting where cost drivers are identified, the objective of TPM is to identify variables that can demonstrate improved performance. All major equipment losses are functionally related to availability, performance, efficiency, and/or quality rate so the improvement resulting from the maintenance system can be measured by its impact on overall equipment effectiveness (see below).

Beneficial results of TPM include:

  • It maximizes overall equipment effectiveness and overall efficiency.
  • It takes the guesswork out of determining which machine needs major repairs or rebuilding.
  • It provides objectivity by converting the operator's intuition into quantifiable values.
  • It pinpoints exact maintenance requirements. The operator carries out only the needed corrective actions, so no unnecessary work, beyond routine maintenance, is done.
  • It rapidly verifies the effectiveness of major corrective work.
  • It helps operators improve their job skills.
  • It motivates operators by involving them in maintenance of their own machines and in team-based concepts.
  • It gives operators ownership of making the project a success by involving them in the process.
  • It enables the development of a preventive maintenance program for the lifecycle of the equipment.
  • It gets everyone involved in equipment design and selection, resulting in a better understanding of why certain decisions and trade-offs are necessary.
  • It results in equipment and maintenance management (inherent in a reliability strategy).
  • It maximizes capacity.
  • It minimizes costs.
  • It improves product quality.
  • It improves safety.
  • It continually improves the manufacturing process.

As a final note on TPM, another school of thought holds that TPM can be adopted by continuous diagnostic monitoring of a machine's conditions and establishing a trend line for it. Trend lines approaching or veering into the domain that identifies poor operating conditions will trigger maintenance action.


It has been assumed that preventive maintenance programs help to ensure reliability and safety of equipment and machinery. However, tests performed by airlines in the mid-1960s showed that scheduled overhaul of complex equipment had little or no positive effect on the reliability of the equipment in service. These tests revealed the need for a new concept of preventive maintenance, which later became known as reliability-centered maintenance (RCM).

The concept of RCM is rooted in a 1968 working paper prepared by the Boeing 747 Maintenance Steering Group. A refined version appeared in 1970. Continued studies at the Department of Defense led to the 1986 publication of the Reliability Centered Maintenance Requirements for Naval Aircraft, Weapons Systems and Support Equipment, a set of maintenance standards and procedures that certain military maintenance personnel were expected to follow. The RCM methodology was further developed and found application not only in the military and aviation, but also in the energy, manufacturing, foundry, and transport industries.

According to Bulmer, the RCM process can be considered as three separate but associated analyses: failure mode and effects analysis, consequence analysis, and task analysis. These analyses consider the specific characteristics and consequences of a failure and attempt to arrive at the optimal solution based on this information.


Total productive maintenance provides a systematic procedure for linking corporate goals to maintenance goals. This procedure calls for the consideration of external and internal corporate environments, and then the development of a basic maintenance policy congruent with the environments. Next key points for maintenance improvement are identified, which result in the definition of target values for maintenance performance. These values, referred to as overall equipment effectiveness (OEE), are a function of equipment availability, quality rate, and equipment performance efficiency, and provide a starting point for developing quantitative variables for relating maintenance measurement and control to corporate strategy.

Essentially, OEE offers a measurement tool that helps identify the real areas of opportunity within an operation. These areas have been termed the six big losses. OEE

allows the firm to break these losses into smaller components to better evaluate the impact the maintenance program is making on the operation. The six losses are:

  1. Breakdowns from equipment failure (unplanned downtime)
  2. Setup and adjustments from product changes and minor adjustments necessary to get the equipment operating properly after the line change
  3. Idling and minor stoppages due to abnormal operation of the equipment causing momentary lapses in production, but not long enough to track as downtime
  4. Reduced speeds, the discrepancy between design and actual speed the equipment operates
  5. Process defects due to scrapped production and defects needing rework
  6. Reduced yield and lost materials during the manufacturing process, from start-up to end of production run

If a company has an OEE of 85 percent or more, then it is considered to be a world-class company.


Two major trends in the development of maintenance management research have been identified: (1) emerging developments and advances in maintenance technology, information and decision technology, and maintenance methods; and (2) the linking of maintenance to quality improvement strategies and the use of maintenance as a competitive strategy.

The first major trend has to do with the impact of artificial intelligence techniques, such as expert systems and neural networks, on the formation of maintenance knowledge in industrial organizations. There is a diverse application of expert systems within the maintenance area. A number of these systems and their applications are listed below:

  • CATSan expert maintenance system for detecting sudden failures in diesel-electric locomotive systems.
  • INNATEan expert system used for electronic circuit diagnosis.
  • FSMan expert system used by Boeing for continuous condition monitoring of aircraft alarms.
  • RLAan expert system developed by Lockheed for repair-level analysis for major parts in an aerospace system.
  • GEMS-TTSan expert system used by AT&T maintenance specialists to isolate faults in communication links.
  • TOPASan expert system that diagnoses transmission and signaling problems in real time that may arise on switched circuits.
  • CHARLEYan expert system used by General Motors to diagnose problems with broken machine tools and to instruct less experienced individuals by providing explanations.
  • XCONan expert system developed by Digital Equipment Corporation (now part of Compaq) for product configuration.

The second major trend is typified by the emergence of total productive maintenance, which must be incorporated into the firm's strategy. In the quest for world-class manufacturing standards, many industries are appreciating the need for efficient maintenance systems that have been effectively integrated with corporate strategy. It is vital that maintenance management becomes integrated with corporate strategy to ensure equipment availability, quality products, on-time deliveries, and competitive pricing. Managerial attitudes have changed toward maintenance because of the emergence of new management philosophies. In addition, social trends such as lack of capital, fluctuations in currencies, competition, quality, and environmental consciousness have also encouraged a new focus on maintenance.

Maintenance continues to be a major area of concern for manufacturers and other forms of business. A study of some seventy manufacturing plants found that over 50 percent of the maintenance work performed by these firms was reactive (run to failure, emergency breakdown). The balance of maintenance work was preventive or period based (25%), predictive or condition based (15%), and proactive or root-caused based (10%). A strong correlation has been found to exist between manufacturing cost reduction and preventive/predictive maintenance. Over a five-year period a study group of companies found that productivity improvements correlated strongly with a number of variables, one of which was preventive/predictive maintenance.

Maintenance Repairs and Inventory Management. Maintenance repair and operations (MRO) inventory handling is one of the most important maintenance processes in business organizations because it is a liability that must be accounted for in management reports of the organization. Since MRO inventory management is an expense (rather than an investment) to business organizations, managers do not give much attention towards supervision of the movements of products that are consumed internally within the organization. However, failure to track the in-house inventory activities leads to mismatch between stocking estimates and the actual types and quantities of stock items required to sustain the short-term and long-term operations of a business organization.

There are various strategies that can be applied to ensure efficiency in the management of MRO inventory. The most commonly used strategy involves assigning stocked products in the MRO inventory into different functional categories. For example, the management can split the MRO inventory into routine maintenance products, non-routine maintenance products which are used on regular predetermined schedules, and unpredictable products of emergency nature. Proper MRO inventory management enables business organizations to control repair and maintenance costs by stocking and tracking only those items that are required by the company.

The continued advancement of information technology has led to increased use of automated systems in (MRO) inventory handling practices in business organizations. Both large scale and small scale manufacturers are gradually optimizing the use of Computer Maintenance Management System (CMMS), a software program that facilitates the automation of logistical procedures in the management of operations and maintenance activities in manufacturing firms. CMMS adoption is a transformational function that involves software installation, system configuration, training of end users, and system implementation.

The implementation phase of CMMS in the organization requires the management to develop appropriate oversight measures to ensure that all personnel who are affected by the system have deep understanding of the procedures that concern changes introduced in the routine work flows, data-capturing processes, report processing requirements, and performance logistics by the aided planning of maintenance. Successful incorporation of CMMS into the MRO inventory practices of a firm leads to efficiency in the performance of a firm's maintenance procedures including preventive maintenance, repair work, and improvement work, as well as routine activities such as inventory control and asset management.

Mike Laskiewicz recommends that organizations recognize maintenance as a key department that needs to be well managed. In addition, the maintenance department should be led by a strong-minded individual who is a good motivator, technically competent, experienced and familiar with advanced industry practices. Finally Laskiewicz notes that maintenance planning must be a top priority.

SEE ALSO Continuous Improvement; Lean Manufacturing and Just-in-Time Production; Operations Strategy; Organizational Culture


Chan, F.T.S., H.C.W. Lau, R.W.L.Ip, H.K. Chan, and S. Kong. Implementation of Total Productive Maintenance: A Case Study. International Journal of Production Economics 95 (2005): 71.

Computer Maintenance Management System Management System. O&M Best Practices. Available from:

Cox, James F., John H. Blackstone, Jr., and Michael S. Spencer, eds. APICS Dictionary. 8th ed. Falls Church, VA: APICS, 1995.

Laskiewicz, Mike. 4 Paths to Engineering, Maintenance Integration. Control Engineering 52, no. 2 (2005): 10.

Lee, Hsu-Hua. A Cost/Benefit Model for Investments in Inventory and Preventive Maintenance in an Imperfect Production System. Computers and Industrial Engineering 48, no. 1 (2005): 55.

Murphy, Frank. Once Organized, a Storeroom Must Be Run Correctly. Facilities Engineering Journal, June 2008. Available from:

Oke, S.A. An Analytical Model for the Optimisation of Maintenance Profitability. International Journal of Productivity and Performance Management 54, no. 1/2 (2005): 113134.

Taninecz, George. Best Practices and Performances. IndustryWeek, 1 December 1997, 2843.

Wen-Jihn, Chen. Minimizing Total Flow Time and Maximum Tardiness with Periodic Maintenance.Journal of Quality Maintenance Engineering, 13 No. 3, 2007: 293303.

Wireman, Terry. Preventive Maintenance. New York: Industrial Press, 2007.

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One of the most striking properties of memory is its extreme duration; people have memories dating as far back as twenty years or more. Similarly, one of the features of long-term potentiation or LTP (at least in certain brain structures) is its duration; it has been a major challenge for neurobiology to provide a cellular mechanism for long-lasting changes in synaptic transmission that outlast protein turnover. The discovery of the critical role of the NMDA receptors in triggering LTP indicated the existence of distinct stages in the establishment of LTP, which are generally defined as induction and maintenance (Bliss and Lynch, 1988). The former refers to events activated during the high-frequency stimulation, whereas the latter designates the processes that are responsible for the changes in synaptic transmission that underlie LTP and their long-term maintenance. In general, three types of mechanisms have been proposed as maintenance mechanisms: those producing increased transmitter release; those resulting in changes in spine electrical properties; and those implicated in regulating receptor properties (Landfield and Deadwyler, 1988). Since the 1980s evidence against and for each of these mechanisms has been obtained, and the most salient features of the arguments are presented in this entry.

Presynaptic Mechanisms

An increase in transmitter release could account for an increase in synaptic transmission; it is generally admitted, for instance, that short-term potentiation is due to increased transmitter release (Zucker, 1989). Biochemical and electrophysiological evidence has been obtained in support of the hypothesis that increased transmitter release accounts for LTP. Glutamate is likely to be the neurotransmitter used by synapses exhibiting LTP in various hippocampal pathways, and increased glutamate levels have been found after LTP induction in perfusates obtained with push-pull cannulas implanted in the dentate gyrus (Dolphin, Errington, and Bliss, 1982). Increased glutamate release was also found after LTP induction in hippocampal slices and in synaptosomes prepared from hippocampus of rats in which LTP had been induced. Since the induction of LTP involves the postsynaptic activation of NMDA receptors, a retrograde signal has been postulated that relays the postsynaptic activation to the presynaptic terminal. Researchers initially proposed arachidonic acid to be such a retrograde signal, since activation of NMDA receptors stimulates phospholipase A2 (PLA2), and PLA2 inhibitors prevent LTP formation (Bliss and Lynch, 1988). Arachidonic acid could also provide a link with the presynaptic machinery involved in the regulation of transmitter release because it activates protein kinases that have been shown to participate in phosphorylation reactions important for transmitter release. Researchers later proposed that nitric oxide as well as carbon monoxide were retrograde signals, although the evidence for this conclusion remains highly controversial (Hawkins, Son, and Arancio, 1998; Malenka and Nicoll, 1999). While this mechanism could conceivably provide a satisfactory explanation for a short-lasting enhancement of transmitter release, in its present version it does not account for a long-lasting increase.

Quantal analysis of synaptic transmission (Martin, 1966) is an approach that, in principle, could provide an unambiguous answer to the question of the locus of the changes underlying LTP. It uses the intrinsic variability of transmitter release and statistical methods to determine the parameters generally thought to govern synaptic transmission; in effect, the probability of release, the number of release sites, and the elementary size of a postsynaptic response elicited by a quantum of neurotransmitter. Three groups have reported results obtained with quantal analysis in field CA1 before and after LTP induction in hippocampal slices. Two groups observed an increase in quantal content (Malinow and Tsien, 1990; Bekkers and Stevens, 1990), whereas one group observed an increase in quantal size (Foster and McNaughton, 1991). In addition to this ambiguity in the results, quantal analysis requires a number of assumptions that might not be satisfied at hippocampal synapses. In particular, several studies have indicated the existence of synapses with functional NMDA receptors but few, if any, functional AMPA receptors (the socalled silent synapses). Transformation of silent synapses into active synapses by LTP-inducing stimulation could account for the inconsistencies in results from quantal analysis (Malenka and Nicoll, 1999).

Finally, increased transmitter release could be accounted for by an increase in the number of synapses. Anatomical studies using quantitative electron microscopy have provided evidence that the number of certain categories of synapses, in particular sessile synapses, is increased in field CA1 following LTP induction (Lee, Schottler, Oliver, and Lynch, 1980; Chang and Greenough, 1984). Although an increased number of synapses could explain the duration of LTP and account for its maintenance, it is not yet clear whether the increase in sessile synapses represents the formation of new synapses or the transformation of existing synapses by shape modifications (Toni et al., 1999).

Changes in Spine Electrical Properties

Since their discovery, there has been much speculation concerning the roles of dendritic spines in synaptic transmission and the possibilities that synaptic plasticity could be due to alterations in their electrical properties (Rall, 1978; Coss and Perkel, 1985). Because of their shape—large heads relative to long, narrow necks—they are considered to be high-resistance elements coupling voltage changes at the synapses with voltage changes in dendritic shafts. Based upon calculation and computer simulation, researchers have proposed that decreased neck resistance could account for increased synaptic responses (Wilson, 1988), which could affect the AMPA receptors more specifically than the NMDA receptors (Lynch and Baudry, 1991). Such a decrease in spine resistance could be due to an increase in neck dimension, and anatomical evidence indicates that LTP is accompanied by an increase in spines with wider and shorter necks. The recent discoveries of active elements (channels or pumps) in dendritic spines provide alternative means of modifying their electrical properties (Johnston, Magee, Colbert, and Cristie, 1996), although there is no evidence that these elements are modified following LTP induction.

Changes in Receptor Properties

One of the most important characteristics of LTP is that it is expressed by an increase in the component of the synaptic response resulting from the activation of the AMPA receptors with little changes in the component generated by the activation of NMDA receptors. Thus an alteration of the properties of the AMPA receptors has been proposed as a potential maintenance mechanism. Several studies have shown that both the ligand binding and the ionic conductance properties of the AMPA receptors are affected by a variety of manipulations. In particular, changes in the lipid environment of the AMPA receptors modify its affinity for agonists, an observation that could account for the involvement of PLA2 in LTP. Studies conducted in the 1990s on the molecular biology of the AMPA receptors have provided exciting results concerning the nature and properties of these receptors. AMPA receptors belong to a family of receptors encoded by at least four related genes, each existing in two closely similar versions generated by alternative splicing of the genes, and designated flip and flop. Researchers have proposed that AMPA receptors exist as oligomers composed of a number of possible arrangements of flip and flop elements, with the flip elements providing larger currents than the flop (Sommer et al., 1990). Twenty-first-century research has suggested that LTP could result from a change in the composition of receptor subunits or in changes in the rates of receptor insertion or internalization in the synaptic membrane from a subsynaptic pool of receptors (Malinow, Mainen, and Hayashi, 2000). Another dimension related to the stabilization of the changes underlying LTP maintenance has recently been included to the search for the mechanisms of LTP. It is now apparent that LTP stabilization involves adhesion molecules and that there is a time window following LTP induction during which processes leading to LTP consolidation can be reversed, thus producing depotentiation (Lynch, 1998). There has been considerable discussion to determine whether depotentiation represents the same process as long-term depression of synaptic transmission. Although both processes share a number of features, there is not yet a general consensus as to the mechanisms and the significance of these forms of synaptic plasticity.


Although several mechanisms discussed in this entry could account for some characteristics of LTP, most of them run into difficulties when they have to explain its stability. This feature is almost certain to eliminate most mechanisms, however attractive they might appear, that are based solely on conformational or posttranslational changes in proteins. In particular, several speculative mechanisms of LTP maintenance have been based on the idea of biochemical switches, constituted of biochemical reactions involving positive feedback. The most popular of these biochemical switches is derived from the properties of autophosphorylation of calcium/calmodulin kinase type II, which is a very prominent protein in postsynaptic densities and especially in hippocampus (Crick, 1984; Lisman, 1994). The mechanism involved in LTP maintenance therefore will probably require structural modifications that can confer lasting stability to biochemical modifications responsible for changes in synaptic transmission. The coupling of these processes with those responsible for the maintenance of the adhesive properties of synaptic contacts represents a key feature in the evolution of adaptive properties of brain neuronal networks. Finally, the various mechanisms described above underline the richness of mechanisms that have evolved to produce synaptic plasticity and that are likely to contribute to the multiple forms of potentiation that are being uncovered at a variety of central synapses.



Bekkers, J. M., and Stevens, C. F. (1990). Presynaptic mechanism for long-term potentiation in the hippocampus. Nature 346, 724-729.

Bliss, T. V. P., and Lynch, M. A. (1988). Long-term potentiation: Mechanisms and properties. In P. W. Landfield and S. A. Deadwyler, eds., Long-term potentiation: From biophysics to behavior. New York: Liss.

Chang, F., and Greenough, W. T. (1984). Transient and enduring morphological correlates of synaptic activity and efficacy change in the rat hippocampal slice. Brain Research 309, 35-46.

Coss, R. G., and Perkel, D. H. (1985). The function of dendritic spines: A review of theoretical issues. Behavior, Neurology, and Biology 44, 151-185.

Crick, F. (1984). Memory and molecular turn-over. Nature 312, 101.

Dolphin, A. C., Errington, M. L., and Bliss, T. V. P. (1982). Long-term potentiation of the perforant path in vivo is associated with increased glutamate release. Nature 297, 496-498.

Foster, T. C., and McNaughton, B. L. (1991). Long-term synaptic enhancement in CA1 is due to increased quantal size, not quantal content. Hippocampus 1, 79-91.

Hawkins, R. D., Son, H., and Arancio, O. (1998). Nitric oxide as a retrograde messenger during long-term potentiation in hippocampus. Progress in Brain Research 118, 155-172.

Johnston, D., Magee, J. C., Colbert, C. M., and Cristie, B. R. (1996). Active properties of neuronal dendrites. Annual Review of Neuroscience 19, 165-186.

Landfield, P. W., and Deadwyler, S. A., eds. (1988). Long-term potentiation: From biophysics to behavior. New York: Liss.

Lee, K., Schottler, F., Oliver, M., and Lynch, G. (1980). Brief bursts of high frequency stimulation produce two types of structural changes in rat hippocampus. Journal of Neurophysiology 44, 247-258.

Lisman, J. (1994). The CaM kinase II hypothesis for the storage of synaptic memory. Trends in Neurosciences 17, 406-412.

Lynch, G. (1998). Memory and the brain: Unexpected chemistries and a new pharmacology. Neurobiology of Learning and Memory 70, 80-100.

Lynch, G., and Baudry, M. (1991). Re-evaluating the constraints on hypotheses regarding LTP expression. Hippocampus 1, 9-14.

Malenka, R. C., and Nicoll, R. A. (1999). Long-term potentiation—a decade of progress? Science 285, 1,870-1,874.

Malinow, R., Mainen, Z. F., and Hayashi, Y. (2000). LTP mechanisms: From silence to four-lane traffic. Current Opinion in Neurobiology 3, 352-357.

Malinow, R., and Tsien, R. W. (1990). Presynaptic enhancement shown by whole-cell recordings of long-term potentiation in hippocampal slices. Nature 346, 177-180.

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Rall, W. (1978). Dendritic spines and synaptic potency. In R. Porter, ed., Studies in Neurophysiology. Cambridge, UK: Cambridge University Press.

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Toni, N., Buchs, P.-A., Nikonenko, I., Bron, C. R., and Muller, D. (1999). LTP promotes formation of multiple spine synapses between an axon terminal and a dendrite. Nature 401, 421-425.

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Zucker, R. S. (1989). Short-term synaptic plasticity. Annual Review of Neuroscience 12, 13-22.



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Maintenance is an important aspect of military logistics and includes those activities needed to keep weapons, vehicles, and other materiel in an operable condition; to restore them to a serviceable condition when necessary; or to improve their usefulness through modifications. Such maintenance activities include inspection, testing, classification as to serviceability, adjustment, servicing, recovery, evacuation, repair, overhaul, and modification. Salvage and disposal are related functions.

Modern military equipment is complex and expensive and must be designed with reliability, durability, and ease of maintenance in mind. Thus, maintenance requirements, the potential usage of repair parts, and the tools and equipment needed to effect repairs are determined during the equipment development process, and operational capabilities must sometimes be sacrificed for greater reliability or ease of maintenance. Life cycle maintenance costs are also an important consideration inasmuch as the lifetime maintenance costs usually exceed an item's initial acquisition cost.

Traditionally, maintenance support has been divided into five levels, or echelons. User (first echelon) maintenance includes inspection, cleaning, tightening, lubrication, and minor adjustments performed by the equipment operator. Organizational (second echelon) maintenance is performed by unit maintenance personnel and involves recovery, evacuation, inspection, troubleshooting, and some replacement of parts and assemblies. Direct support (third echelon) maintenance is carried out by specialized maintenance units in fixed or semimobile maintenance facilities—or by mobile teams—and involves recovery, evacuation, inspection, replacement of major parts and assemblies, and the repair of some assemblies. Items repaired at the direct support level are normally returned to the using unit. General support (fourth echelon) maintenance involves the systematic repair and rebuilding of equipment and is generally performed by highly specialized maintenance units in fixed general support technical centers, each of which specializes in a particular type of equipment (e.g., combat vehicles or missiles). Items repaired or rebuilt at the general support level are returned to general stocks rather than to the using unit. Depot (fifth echelon) maintenance is also carried out by highly specialized maintenance personnel in fixed facilities; it involves the complete rebuilding of entire items and the renovation of major assemblies (such as motors or transmissions) for return to general stocks.

In recent years, the armed services have streamlined the maintenance process and now recognize only three echelons: user/direct support, intermediate/general support, and wholesale. In practice, the type and amount of work to be accomplished at each level is determined by the missions of the units involved, the probable operational situation, and the most cost‐effective use of available maintenance resources. The thrust of modern maintenance doctrine is to perform maintenance functions as far forward on the battlefield as possible by employing mobile repair teams, rapid battlefield recovery, and cannibalization (the reuse of serviceable parts taken from an otherwise unrepairable item). In general, it is easier and quicker to maintain a piece of equipment in a fully equipped fixed maintenance shop rather than in the field, but by maintaining equipment as far forward as possible, evacuation and repair time is minimized. Thus, the time an item is available to perform its combat function is increased.

Although some common maintenance support is provided by the General Services Administration and the Defense Logistics Agency, each of the armed services has its own system to provide every level of maintenance support. Army wholesale maintenance activities are overseen by the U.S. Army Materiel Command, which controls seven commodity‐oriented subordinate commands, each of which specializes in a particular type of materiel (e.g., wheeled vehicles or communications‐electronics equipment). Most army units, including maintenance units themselves, are organized with organic maintenance personnel and equipment. Thus, an infantry company normally has an organic maintenance section and an infantry division has an organic direct support maintenance battalion. Intermediate/general support maintenance activities are usually controlled by combat service support commands (e.g., a corps support command or a theater army area command).

The U.S. Marine Corps operates two distinct maintenance systems of its own, although the navy provides aviation and medical supply and maintenance support. Marine Corps base maintenance activities provide all levels of support for commercial‐type equipment or contract out what is beyond their capability. Fleet Marine Force units are supported by a system similar to that of army field forces, with organic maintenance units backed by specialized direct and general support maintenance units. Wholesale maintenance activities are carried out at Marine Corps logistics bases in Georgia and California.

Responsibility for navy maintenance activities is assigned to the Navy Systems Command, which oversees a number of specialized commodity‐oriented commands (e.g., the Naval Air Systems Command for naval aviation repair and the Naval Sea Systems Command for shipyards and ship repair facilities). User/direct support–level maintenance is performed by the using ship or air squadron. Intermediate/general support–level maintenance is performed in local repair facilities, which include combat logistics force ships and overseas bases. Wholesale‐level maintenance is performed in navy or commercial facilities in the continental United States.

Air force maintenance activities are the responsibility of the Air Force Logistics Command, which monitors the operation of five Air Logistics Centers. These centers, located in Georgia, Oklahoma, Texas, Utah, and California, are centralized wholesale repair facilities. Retail aircraft maintenance is performed at air base level. For nontactical (transport and utility) aircraft, a centralized concept is employed, and the work is normally performed in fixed base maintenance facilities by air force maintenance squadrons. Tactical aircraft are also maintained by air force maintenance squadrons, using a more decentralized concept designed to produce the maximum number of combat sorties.

Effective and cost‐efficient maintenance systems are essential to the success of military forces on land, at sea, and in the air. The complexity of modern weapons systems and the large number of such systems deployed in all types of climatic and terrain require extraordinarily good design and effective maintenance procedures and personnel if they are to perform their intended functions. The ability to ensure that weapons, vehicles, and other equipment are available and function properly gives a military force a decided advantage over an opponent who does not have that ability.
[See also Weaponry.]


Headquarters, Department of the Army , The Department of the Army, 1977.
Headquarters, Department of the Army , Field Manual 54‐10: Logistics—An Overview of the Total System, 1977.
United States Army War College, Department of Military Strategy, Planning, and Operations , Materiel Logistics—Service Logistics: Concepts, Organization, and Planning, 1991.

Charles R. Shrader

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maintenanceabeyance, conveyance, purveyance •creance • ambience •irradiance, radiance •expedience, obedience •audience •dalliance, mésalliance •salience •consilience, resilience •emollience • ebullience •convenience, lenience, provenience •impercipience, incipience, percipience •variance • experience •luxuriance, prurience •nescience • omniscience •insouciance • deviance •subservience • transience •alliance, appliance, compliance, defiance, misalliance, neuroscience, reliance, science •allowance •annoyance, clairvoyance, flamboyance •fluence, pursuance •perpetuance • affluence • effluence •mellifluence • confluence •congruence • issuance • continuance •disturbance •attendance, dependence, interdependence, resplendence, superintendence, tendance, transcendence •cadence •antecedence, credence, impedance •riddance • diffidence • confidence •accidence • precedence • dissidence •coincidence, incidence •evidence •improvidence, providence •residence •abidance, guidance, misguidance, subsidence •correspondence, despondence •accordance, concordance, discordance •avoidance, voidance •imprudence, jurisprudence, prudence •impudence • abundance • elegance •arrogance • extravagance •allegiance • indigence •counter-intelligence, intelligence •negligence • diligence • intransigence •exigence •divulgence, effulgence, indulgence, refulgence •convergence, divergence, emergence, insurgence, resurgence, submergence •significance •balance, counterbalance, imbalance, outbalance, valance •parlance • repellence • semblance •bivalence, covalence, surveillance, valence •sibilance • jubilance • vigilance •pestilence • silence • condolence •virulence • ambulance • crapulence •flatulence • feculence • petulance •opulence • fraudulence • corpulence •succulence, truculence •turbulence • violence • redolence •indolence • somnolence • excellence •insolence • nonchalance •benevolence, malevolence •ambivalence, equivalence •Clemence • vehemence •conformance, outperformance, performance •adamance • penance • ordinance •eminence • imminence •dominance, prominence •abstinence • maintenance •continence • countenance •sustenance •appurtenance, impertinence, pertinence •provenance • ordnance • repugnance •ordonnance • immanence •impermanence, permanence •assonance • dissonance • consonance •governance • resonance • threepence •halfpence • sixpence •comeuppance, tuppence, twopence •clarence, transparence •aberrance, deterrence, inherence, Terence •remembrance • entrance •Behrens, forbearance •fragrance • hindrance • recalcitrance •abhorrence, Florence, Lawrence, Lorentz •monstrance •concurrence, co-occurrence, occurrence, recurrence •encumbrance •adherence, appearance, clearance, coherence, interference, perseverance •assurance, durance, endurance, insurance •exuberance, protuberance •preponderance • transference •deference, preference, reference •difference • inference • conference •sufferance • circumference •belligerence • tolerance • ignorance •temperance • utterance • furtherance •irreverence, reverence, severance •deliverance • renascence • absence •acquiescence, adolescence, arborescence, coalescence, convalescence, deliquescence, effervescence, essence, evanescence, excrescence, florescence, fluorescence, incandescence, iridescence, juvenescence, luminescence, obsolescence, opalescence, phosphorescence, pubescence, putrescence, quiescence, quintessence, tumescence •obeisance, Renaissance •puissance •impuissance, reminiscence •beneficence, maleficence •magnificence, munificence •reconnaissance • concupiscence •reticence •licence, license •nonsense •nuisance, translucence •innocence • conversance • sentience •impatience, patience •conscience •repentance, sentence •acceptance • acquaintance •acquittance, admittance, intermittence, pittance, quittance, remittance •assistance, coexistence, consistence, distance, existence, insistence, outdistance, persistence, resistance, subsistence •instance • exorbitance •concomitance •impenitence, penitence •appetence •competence, omnicompetence •inheritance • capacitance • hesitance •Constance • importance • potence •conductance, inductance, reluctance •substance • circumstance •omnipotence • impotence •inadvertence • grievance •irrelevance, relevance •connivance, contrivance •observance • sequence • consequence •subsequence • eloquence •grandiloquence, magniloquence •brilliance • poignance •omnipresence, pleasance, presence •complaisance • malfeasance •incognizance, recognizance •usance • recusance

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Unauthorized intervention by a nonparty in a lawsuit, in the form of financial or other support and assistance to prosecute or defend the litigation. The preservation of an asset or of a condition of property by upkeep and necessary repairs.

A periodic monetary sum paid by one spouse for the benefit of the other upon separation or the dissolution of marriage; also calledalimonyor spousal support.

At common law the offense of champerty and maintenance arose when a stranger bargained with a party to a legal action, undertaking to pay for the litigation in exchange for a promise of a portion of the recovery. The common-law doctrines of champerty and maintenance were designed to stop vexatious and speculative litigation supported by officious intermeddlers (nonparties with improper motives). These common-law principles have been adopted in varying degrees in the United States, depending on the particular state.

The term maintenance is also used to describe the expenses of preserving property, which may be deductible according to the applicable state or federal tax laws. Maintenance expenses are typically recurring, with the goal of preserving the particular asset in its original condition, to prolong its useful life. Maintenance differs from a repair because a repair is an expenditure designed to return an asset to its normal operating condition.

In family lawmaintenance is often used as a synonym for spousal support or alimony, and the term is in fact replacing alimony. Traditionally, alimony was solely the right of the wife to be supported by the husband. In Orr v. Orr, 440 U.S. 268, 99 S. Ct. 1102, 59 L. Ed. 2d 306 (1979), the U.S. Supreme Court held that an Alabama statute (Ala. Code § 30-2-51 to 30-2-53 [1975]) that provided that only husbands could be required to pay alimony violated the equal protection clause of the fourteenth amendment. Under current law alimony may be payment by either the wife or the husband in support of the other.

The award of spousal maintenance is generally determined based on all or some of the following guidelines: the recipient's financial needs; the payer's ability to pay; the age and health of the parties; the standard of living the recipient became accustomed to during the marriage; the length of the marriage; each party's ability to earn and be self-supporting; and the recipient's nonmonetary contributions to the marriage.

The amount and length of spousal maintenance payments may be agreed to by the parties and approved of by the court, or may be set by the court when the issue is contested. Some states have adopted financial schedules to help judges determine the appropriate level of support. Although maintenance generally takes the form of periodic payments of money directly to the recipient, it can also constitute a payment to a third party to satisfy an obligation of the receiving spouse. Maintenance may be set in a predetermined amount, such as $1,000 a month, or it may be a fluctuating percentage, such as 25 percent of the payer's gross income.

Spousal maintenance may be temporary or permanent. The parties generally may adjust its amount at a future date by returning to court and reassessing the relevant criteria at that time. In some states the parties may forever waive their right to spousal maintenance by written agreement.

Spousal maintenance payments always cease upon the death or remarriage of the recipient. Some states have adopted laws that provide for the termination of maintenance when the payer can show that the recipient is living with another person as if married, but has not remarried because he or she wants to continue to receive maintenance payments. Maintenance also generally terminates upon the death of the payer, although a minority of states will grant the receiving spouse a claim on the estate of the paying spouse. Alternatively, many states require the paying spouse to carry insurance on his or her life, payable to the recipient spouse, in lieu of granting the recipient the right to make a claim on the payer's estate.

Spousal maintenance that is periodic and made in discharge of a legal obligation is included in the gross income of the recipient and is deductible by the payer. Other voluntary payments, made by one spouse to the other, are not treated the same way by the tax code.

further readings

Cornick, Matthew S. 1995. A Practical Guide to Family Law. St. Paul, Minn.: West.



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main·te·nance / ˈmānt(ə)nəns; ˈmāntn-əns/ • n. 1. the process of maintaining or preserving someone or something, or the state of being maintained: crucial conditions for the maintenance of democratic government. ∎  the process of keeping something in good condition: car maintenance | [as adj.] essential maintenance work. 2. the provision of financial support for a person's living expenses, or the support so provided. ∎  alimony or child support. ∎  hist. Law the former offense of aiding a party in a legal action without lawful cause.

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1. (hardware maintenance) The performance of preventive or remedial maintenance on hardware in order to anticipate the onset of incipient faults or to correct a failure due to a hardware fault.

2. See software maintenance.