An ELT Glossary The bare infinitive

The bare infinitive is the base form of the verb used without the infinitive particle to. It may be used :

a) After the dummy operator do. Examples :

I do like those shoes
He didn't see her

b) Following a modal auxiliary. Examples :

We must go.
We can start now

c) After certain other verbs including, make, have, let, help and verbs of perception. Examples :

He made her go.
She had him mow the lawn
He helped her pack
She felt him touch her arm.
They heard the car start.

d) After the expressions  had better / had rather. Examples :

You had better leave
I'd rather not go