A day is one of the seven twenty-four hour periods of time in a week.

Day is the time when it is light, or the time when you are up and doing things.

You can refer to a particular period in history as a particular day or as particular days .

If something happens day after day, it happens every day without stopping.

In this day and age means in modern times.

If you say that something has seen better days, you mean that it is old and in poor condition.

If you call it a day, you decide to stop what you are doing because you are tired of it or because it is not successful.

If someone carries the day, they are the winner in a contest such as a battle, debate, or sporting competition.

If you say that something has had its day, you mean that the period during which it was most successful or popular has now passed.

If something makes your day, it makes you feel very happy.

If something happens day and night or night and day, it happens all the time without stopping.

One day or some day or one of these days means at some time in the future.

If you say that something happened the other day, you mean that it happened a few days ago.

If someone or something saves the day in a situation which seems likely to fail, they manage to make it successful.

If something happens from day to day or day by day, it happens each day.

If it is a month or a year to the day since a particular thing happened, it is exactly a month or a year since it happened.

To this day means up until and including the present time.

If a particular person, group, or thing wins the day, they win a battle, struggle, or competition. If they lose the day, they are defeated.

If you say that a task is all in a day's work for someone, you mean that they do not mind doing it although it may be difficult, because it is part of their job or because they often do it.