day

UK: /ˈdeɪ/ US: /deɪ/ ,(dā)

WordReference Random House Learner's Dictionary of American English © 2025

day /deɪ/   n. [countable]

1. the time between sunrise and sunset:
   I work most of the day at the office and most of the night at home.
2. the light of day;
   daylight:
   In Tanzania the days are as long as the nights.
3. Astronomy a division of time equal to 24 hours, from one midnight to the next:
   seven days in one week.
4. Astronomy a similar division of time for another planet:
   the Martian day.
5. the portion of a day in which one works:
   put in an eight-hour day.
6. a particular date, period, or time:
   in olden days; What day is her birthday?
7. a time thought to provide benefit or opportunity:
   His day will come.
8. Usually, days. period of life:
   His days are numbered.
9. a particular period of time:
   In my day we called them motorcars.
10. [ often: the + ~] the contest or battle going on at the moment:
    to win the day.

Idioms

11. Idioms call it a day, to stop working for the rest of the day:
    Let's call it a day; we've worked eighteen hours.
12. Idioms day in, day out, every day without fail;
    regularly. Also, day in and day out:
    Her constant nagging, day in and day out, is driving me crazy.
13. make someone's day, to make someone very happy or pleased:
    Seeing my kids smile just makes my day.

WordReference Random House Unabridged Dictionary of American English © 2025

day  (dā), n. 

1. the interval of light between two successive nights;
   the time between sunrise and sunset:
   Since there was no artificial illumination, all activities had
   to be carried on during the day.
2. the light of day;
   daylight:
   The owl sleeps by day and feeds by night.
3. Astronomy
   • Also called mean solar day. a division of time equal to 24 hours and representing the average length of the period during which the earth makes one rotation on its axis.
   • Also called solar day. a division of time equal to the time elapsed between two consecutive returns of the same terrestrial meridian to the sun.
   • Also called civil day. a division of time equal to 24 hours but reckoned from one midnight to the next. Cf. lunar day, sidereal day.
4. Astronomy an analogous division of time for a planet other than the earth:
   the Martian day.
5. the portion of a day allotted to work:
   an eight-hour day.
6. a day on which something occurs:
   the day we met.
7. (often cap.) a day assigned to a particular purpose or observance:
   New Year's Day.
8. a time considered as propitious or opportune:
   His day will come.
9. a day of contest or the contest itself:
   to win the day.
10. Often, days. a particular time or period:
    the present day; in days of old.
11. Usually, days. period of life or activity:
    His days are numbered.
12. period of existence, power, or influence:
    in the day of the dinosaurs.
13. Architecture light¹ (def. 19a).
14. Idioms call it a day, to stop one's activity for the day or for the present;
    quit temporarily:
    After rewriting the paper, she decided to call it a day.
15. Idioms day in, day out, every day without fail;
    regularly:
    They endured the noise and dirt of the city day in, day out.
    Also, day in and day out. 

• bef. 950; Middle English; Old English dæg; cognate with German Tag

Day  (dā), n. 

Clarence (Shep•ard)  (shep′ərd), 1874–1935, U.S. author.
1. Biographical Dorothy, 1897–1980, U.S. Roman Catholic social activist, journalist, and publisher.

Collins Concise English Dictionary © HarperCollins Publishers::

day / deɪ/ noun

1. Also called: civil day the period of time, the calendar day, of 24 hours' duration reckoned from one midnight to the next
2. the period of light between sunrise and sunset, as distinguished from the night
3. (as modifier): the day shift
4. the part of a day occupied with regular activity, esp work: he took a day off
5. (sometimes plural) a period or point in time: he was a good singer in his day, in days gone by, any day now
6. the period of time, the sidereal day, during which the earth makes one complete revolution on its axis relative to a particular star. The mean sidereal day lasts 23 hours 56 minutes 4.1 seconds of the mean solar day
7. the period of time, the solar day, during which the earth makes one complete revolution on its axis relative to the sun. The mean solar day is the average length of the apparent solar day and is some four minutes (3 minutes 56.5 seconds of sidereal time) longer than the sidereal day
8. the period of time taken by a specified planet to make one complete rotation on its axis: the Martian day
9. (often capital) a day designated for a special observance, esp a holiday: Christmas Day
10. all in a day's work ⇒ part of one's normal activity; no trouble
11. at the end of the day ⇒ in the final reckoning
12. back in the day ⇒ in the past
13. day of rest ⇒ the Sabbath; Sunday
14. end one's days ⇒ to pass the end of one's life
15. every dog has its day ⇒ one's luck will come
16. in this day and age ⇒ nowadays
17. it's early days ⇒ it's too early to tell how things will turn out
18. late in the day ⇒ very late (in a particular situation)
19. too late
20. that will be the day ⇒ I look forward to that
21. that is most unlikely to happen
22. a time of success, recognition, power, etc: his day will soon come
23. a struggle or issue at hand: the day is lost
24. the ground surface over a mine
25. (as modifier): the day level
26. from day to day ⇒ without thinking of the future
27. call it a day ⇒ to stop work or other activity
28. day after day ⇒ without respite; relentlessly
29. day by day ⇒ gradually or progressively; daily: he weakened day by day
30. day in, day out ⇒ every day and all day long
31. from Day 1, from Day One ⇒ from the very beginning
32. one of these days ⇒ at some future time
33. (modifier) of, relating to, or occurring in the day: the day shift

Related adjective(s): diurnal

Etymology: Old English dæg; related to Old High German tag, Old Norse dagr

Collins Concise English Dictionary © HarperCollins Publishers::

Day / deɪ/ noun

1. Doris, born Doris Kappelhoff. 1924–2019, US actress and singer; noted for her roles in musicals, romances, and comedies; her films include Calamity Jane (1953) and Pillow Talk (1959)
2. Sir Robin. 1923–2000, British radio and television journalist, noted esp for his political interviews