The word reason is used in many idiomatic expressions. Here is a list of them.

All the more reason

This expression is used to emphasize the reason for doing something.

A: Sam is very weak in mathematics.

B: All the more reason for working harder at it.

Jack: I’m tired of painting this cupboard. It’s so old and rotting.

Mary: All the more reason for painting it.

Due to / for reasons beyond one’s control

If something happens for reasons beyond your control, you are not responsible for it.

• Due to reasons beyond our control, we have not been able to ship the item.

For no reason / For no apparent reason

If something happens for no reason, it happens without an obvious cause.

• Sometimes she would cry for no apparent reason.

For one reason or another

This expression is used for saying that there is more than one reason for (doing) something.

• Her books are always, for one reason or another, best sellers.

For reasons best known to himself / herself

This expression is used for saying that you don’t know the reason why someone does something.

• Susan, for reasons best known to herself, kept to herself.

For some reason

This expression is used for saying that you don’t know why something happened.

• For some reason, I don’t like her.

Give me one good reason

This expression is also used for emphasizing that there is a good reason for doing something.

• He has stolen money before, so give me one good reason why we shouldn’t dismiss him.

Have your reasons

When you have your reasons to do something, you do not want to discuss it with anyone.

• I have my reasons to quit that job.

No reason

This expression is used when you do not want to tell someone why you have done something.

• ‘Why did you shout at her?’ ‘No reason.’ (= I don’t want to tell you why I shouted at her.)

The reason behind something

The reason behind something is the real cause of it.

• The reason behind his disappearance was never known.