Definition of day
1a
: the time of light between one night and the next
the shortest day of the year
b
: daylight sense 1
woke up at the break of day
c
: daytime
sleeps during the day and works at night
2
astronomy
: the period of rotation of a planet (such as earth) or a moon on its axis
the length of one day on Mars
3
: the mean solar day of 24 hours beginning at midnight by mean time
open seven days a week the first day of every month Take one pill two times a day.
4
: a specified day or date
their wedding day the day of her birth
5
: a specified time or period : age
in grandfather's day
—often used in plural the old daysthe days of sailing ships
6
: the conflict or contention of the day
played hard and won the day
7
: the time established by usage or law for work, school, or business
starts his day with a cup of coffee after a long day at school We have a busy day tomorrow.
day after day
day in, day out
: for an indefinite or seemingly endless number of days
wore the same pants day after day
: for an indefinite number of successive days
does the same thing at work day in, day out
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Merriam-Webster unabridged
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Time Traveler for day
The first known use of day was before the 12th century
See more words from the same century