Grammar

Must and Mustn't

Use 'must' to express strong obligation or a firm recommendation, and 'mustn't' for prohibition. It is followed by the base verb and does not change for different subjects.

Post

Level A2 Modals

Summary

Use 'must' to express strong obligation or a firm recommendation, and 'mustn't' for prohibition. It is followed by the base verb and does not change for different subjects.

Structure

subject + must/mustn't + base verb

Examples

Common mistakes

• Thinking 'mustn't' means 'don't need to' — it means prohibition, not absence of obligation.
• Adding 'to', e.g. 'You must to go' instead of 'You must go'.

Related

Have To and Don't Have To Should for Advice

More modals

Can / Could (Ability and Permission) A2

Use 'can' for present ability and informal permission or requests. Use 'could' for past ability and for more polite requests.

Must / Have To (Obligation) B1

Use 'must' and 'have to' to express obligation or necessity. 'Mustn't' means something is forbidden, while 'don't have to' means there is no obligation.

May / Might (Possibility) B1

Use 'may' and 'might' to talk about present or future possibility. 'May' is also used for formal permission.

Would for Past Habits B2

Use 'would' to talk about repeated past actions and habits, similar to 'used to'. Unlike 'used to', 'would' is not normally used for past states.

Would (Polite Requests and Hypotheticals) B1

Use 'would' for polite requests and offers, for hypothetical results (especially in conditionals), and to describe imagined situations.

Can and Can't for Ability A1

Use 'can' to say someone is able to do something and 'can't' for inability. 'Can' is followed by the base form of the verb and stays the same for all subjects.

External links

markdown