Grammar

Modals of Deduction (Past)

These structures express how certain we are about a past situation. 'Must have' shows we are sure it happened, 'might/may/could have' show it possibly happened, and 'can't have' shows we are sure it didn't.

Post

Level B2 Modals

Summary

These structures express how certain we are about a past situation. 'Must have' shows we are sure it happened, 'might/may/could have' show it possibly happened, and 'can't have' shows we are sure it didn't.

Structure

must / might / may / could / can't + have + past participle

Examples

The road is wet; it must have rained overnight.
She might have missed the train.
He can't have finished already; it's only been five minutes.
They could have taken the wrong turning.

Common mistakes

• Writing 'must of' instead of 'must have'.
• Using 'mustn't have' for negative certainty: prefer 'can't have'.

Related

Modals of Deduction (Present) Should Have / Ought to Have

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

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