Modal verbs

Modal auxiliary verb

A helping verb that modifies the main verb to convey concepts such as ability, permission, necessity, or possibility.

Bare infinitive rule

The bare infinitive rule states that certain verbs, especially modal auxiliary verbs, are followed by the base form of the main verb without the particle 'to.'

Modal verb indicating current ability or informal permission

Can

Modal verb indicating strong obligation or logical necessity

Must

Modal verb used to give advice or express mild obligation

Should

Modal verb indicating formal permission or slight

Undefined