This subjunctive has three uses: (1) Mandative. Mainly in subordinate clauses, following a verb, adjective, or noun expressing a past or present command, suggestion, or other theoretical possibility: I insist that she disband the team; It is essential that it be disbanded; She ignored his request that she disband the team. When a negative is used with this subjunctive, it precedes the verb: He requested that she not embarrass him, except with be when not be and be not are both possible: He was anxious that his name be not/not be brought into disrepute. The mandative subjunctive is commoner in AmE than BrE, but appears to be on the increase in BrE. In both, but especially in BrE, it can be replaced by a should- construction or an indicative: He requested that she should not embarrass him; He was anxious that his name was not brought into disrepute. (2) Conditional and concessive. Sometimes formally in subordinate clauses of condition or concession: If music be the food of love, play on …; Whether that be the case or not …; Though he ask a thousand times, the answer is still NO. The alternatives are an indicative or a should-phrase: If music is …; Though he should ask … This usage does not extend to past time. (3) Formulaic. In independent clauses mainly in set expressions. Some follow normal subject–verb word order (God save the Queen! Heaven forbid!), while others have inversion of main verb and subject (Long live the Queen!; Far be it from me to interfere). Come plus a subject introduces a subordinate clause: Come the end of the month, (and) there'll be more bills to pay.
The ‘past’ subjunctive is now often called the were-subjunctive, because this is the only form in which there is a distinction from the indicative, and then only in the first- and third-person singular: If I were you … as opposed to If I was you. It is used with present and future (not past) reference in various hypothetical clauses, including condition: If only I were young again; If he were asked, he might help; This feels as if it were wool; I wish she were here now; Suppose this were discovered; I'd rather it were concealed. In popular and non-formal speech and writing, the were-subjunctive is often replaced by the indicative was, which brings this verb into line with other verbs, where the past tense is similarly used for hypotheses about the present and future: If only I knew how; I'd rather you said nothing. Were is, however, widely preferred in If I were you … In the fixed phrase as it were (He's captain of the ship, as it were), were cannot be replaced by was. The use of were instead of was to refer to a real past possibility is generally considered an over-correction: *If I were present on that occasion, I remember nothing of it. This contrasts with the purely hypothetical past, If I had been present … , which strongly implies but I was not.
sub·junc·tive / səbˈjəng(k)tiv/ Gram. • adj. relating to or denoting a mood of verbs expressing what is imagined or wished or possible. Compare with indicative. • n. a verb in the subjunctive mood. ∎ (the subjunctive) the subjunctive mood. DERIVATIVES: sub·junc·tive·ly adv.