day / dā/ • n. 1. a period of twenty-four hours as a unit of time, reckoned from one midnight to the next, corresponding to a rotation of the earth on its axis. ∎ the part of this period when it is light; the time between sunrise and sunset. ∎ the time spent working during such a period: he works an eight-hour day. ∎ Astron. a single rotation of a planet in relation to its primary. ∎ Astron. the period on a planet when its primary star is above the horizon. ∎ archaic daylight: it was broad day. 2. (usu. days) a particular period of the past; an era: the laws were very strict in those days. ∎ (the day) the present time: the issues of the day. ∎ a day associated with a particular event or purpose: graduation day. ∎ a day's endeavor, or the period of an endeavor, esp. as bringing success: speed and surprise would win the day. ∎ (days) a particular period in a person's life or career: my student days. ∎ (one's day) the successful, fortunate, or influential period of a person's life or career: a matinée idol in his day. ∎ (one's days) the span of someone's life: she cared for him for the rest of his days.• adj. carried out during the day as opposed to the evening or at night: my day job. ∎ (of a person) working during the day as opposed to at night: a day nurse.PHRASES: all in a (or the) day's work (of something unusual or difficult) accepted as part of a normal routine or as a matter of course: dodging sharks is all in a day's work for these scientists.any day inf. at any time: you can take me dancing any day of the week. ∎ (used to express one's strong preference for something) under any circumstances: I'd rather live in a shack in the woods, any day. ∎ very soon: she's expected to give birth any day.at the end of the day see end.by the day gradually and steadily: growing by the day.call it a day end a period of activity, esp. resting content that enough has been done. day after day on each successive day, esp. over a long period: the rain poured down day after day.day and night all the time. day by day gradually and steadily. day in, day out continuously or repeatedly over a long period of time.day of reckoning the time when past mistakes or misdeeds must be punished or paid for; a testing time when the degree of one's success or failure will be revealed.from day one from the very beginning. have had one's (or its) day be no longer popular, successful, or influential. if someone is a day at least (added to a statement about a person's age): he must be seventy if he's a day.in this day and age at the present time; in the modern era. not someone's day used to convey that someone has had a bad day.—— of the day a thing currently considered to be particularly interesting or important: the big story of the day.one day (or one of these days) at some time in the future. one of those days a day when several things go wrong.that will (or that'll) be the day inf. that will never happen.these days at present. those were the days used to assert that a particular past time was better than the present.to the day exactly: four years to the day.to this day up to the present time; still.
be the day weary or be the day long, at last it ringeth to evensong even the most difficult time will come to an end; saying recorded from the early 16th century.
day of reckoning the time when past mistakes or misdeeds must be punished or paid for, a testing time when the degree of one's success or failure will be revealed; with allusion to Judgement Day, on which (in some beliefs) the judgement of mankind is expected to take place.
day-star the morning star, (in poetic use) the sun; figuratively, someone or something regarded as the precursor of a new era.
don't give up the day job don't recklessly abandon steady work with the idea of making a fortune by pursuing a hobby or alternative interest. Used as a humorous way of recommending someone not to pursue an alternative (and perhaps more glamorous) career at which they are unlikely to be successful.
See also days, every dog has his day, make someone's day, a rainy day, red-letter day, Rome was not built in a day, tomorrow is another day, a year and a day.