If something is deep, it extends a long way down from the ground or from the top surface of something.

A deep container, such as a cupboard, extends or measures a long distance from front to back.

You use deep to talk or ask about how much something measures from the surface to the bottom, or from front to back.

Deep in an area means a long way inside it

In sports such as football and tennis, a deep shot or pass is one that sends the ball a long way towards the end of the pitch or court.

If you say that things or people are two ,three, or four deep, you mean that there are two, three, or four rows or layers of them there.

You use deep to emphasize the seriousness, strength, importance, or degree of something.

If you are in a deep sleep, you are sleeping peacefully and it is difficult to wake you.

If you are deep in thought or deep in conversation, you are concentrating very hard on what you are thinking or saying and are not aware of the things that are happening around you.

A deep look seems to see right into your mind.

A deep breath or sigh uses or fills the whole of your lungs.

You use deep to describe colours that are strong and fairly dark.

A deep sound is low in pitch.

If you describe someone as deep, you mean that they are quiet and reserved in a way that makes you think that they have good qualities such as intelligence or determination.

If you describe something such as a problem or a piece of writing as deep, you mean that it is important, serious, or complicated.

If you are deep in debt, you have a lot of debts.

The deep means the sea.

If you know something deep down or deep down inside, you know that it is true, but you are not always conscious of it or willing to admit it to yourself.

If you say that you took a deep breath before doing something dangerous or frightening, you mean that you tried to make yourself feel strong and confident.

If you say that something goes deep or runs deep, you mean that it is very serious or strong and is hard to change.