Modal Verbs Study Guide

Can

Modal verb indicating ability, permission, or possibility.

Could

Past tense of "can," indicating past ability or polite request.

Should

Modal verb used for advice, recommendations, and expectations.

Should have

Past tense structure indicating criticism or regret about past actions.

Would

Modal verb for polite requests, habitual actions, and hypothetical situations.

Would have

Past tense structure for polite requests or hypothetical situations in the past.

Must

Modal verb expressing necessity, strong recommendation, or logical deduction.

Must have

Past tense structure indicating necessity or logical deduction in the past.

Ought to

Modal verb indicating moral obligation or advice.

Ought to have

Past tense structure indicating criticism or regret about past actions.

Need to

Modal verb expressing necessity and obligation.

Needed to

Past tense structure indicating necessity or obligation in the past.

Had better

Modal verb for strong advice or warning.

Had better have

Rarely used past tense structure for advising or warning about past actions.

Modal verbs

Auxiliary verbs that express necessity, possibility, permission, ability, or obligation.

Key characteristics

Modal verbs have no infinitive form, no -s form, and are followed by the base form of the main verb.

Negative forms

Formed by adding "not" after the modal verb.

Questions

Formed by inverting the subject and the modal verb.