English definition of “day”
24 HOURS [C] › a period of 24 hours: the days of the week January has 31 days. Matthew runs five miles every day. I saw her the day before yesterday.
LIGHT HOURS [C, U] › the period during the day when there is light from the sun: a bright, sunny day We've been travelling all day. These animals sleep during the day and hunt at night.
WORK HOURS [C] › the time that you usually spend at work or school: She's had a very busy day at the office.
the other day › a few days ago: I saw Terry the other day.
day after day › every day for a long period of time: Day after day they marched through the mountains.
one day › used to talk about something that happened in the past: One day, I came home to find my windows smashed.
one day/some day/one of these days › used to talk about something you think will happen in the future: One of these days I'll tell her what really happened.
days › used to talk about a particular period of time when something happened or existed: in my younger days This book was written before the days of computers. › a long time: I haven't seen Jack for days.
these days › used to talk about the present time: I don't go out much these days.
in those days › used to talk about a period in the past: In those days, boys used to wear short trousers.
the old days › a period in the past → See also April Fool's Day → See also Boxing Day → See also Christmas Day → See also at the end of the day → See also field day → See also Independence Day → See also Mother's Day → See also New Year's Day → See also open day → See also polling day → See also Valentine's Day