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.

the light of day; daylight

The owl sleeps by day and feeds by night.

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. Compare lunar day , sidereal day .

an analogous division of time for a planet other than the earth

the Martian day.

the portion of a day allotted to work

an eight-hour day.

a day on which something occurs

the day we met.

( often initial capital letter ) a day assigned to a particular purpose or observance

New Year's Day.

a time considered as propitious or opportune

His day will come.

a day of contest or the contest itself

to win the day.

Often, days. a particular time or period

the present day; in days of old.

Usually, days. period of life or activity

His days are numbered.

period of existence, power, or influence

in the day of the dinosaurs.

light 1 ( def. 19a ) . ?

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.

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.

noun

evening , night

noun

astronomical day , bright , dawn-to-dark , daylight , daytime , diurnal course , early bright , light , light of day , mean solar day , nautical day , sidereal day , sunlight , sunrise-to-sunset , sunshine , working day , age , ascendancy , cycle , epoch , generation , height , heyday , period , prime , term , time , years , zenith , duration , existence , lifetime , span , era , date , equinox , nycthemeron , solstice