[countable] [usually singular] the period of time when you are awake and doing things every day:
You should try to go for a walk every day.
all day (long):
What do you do at home all day?
a day off (=a day when you do not work):
I’ve got a day off next week.
a day out (=a day when you go out somewhere for fun or enjoyment):
All children enjoy a day out at the fair.
Synonyms and related words