English grammar: Modal verbs for deduction

What this grammar point covers

Modal verbs for deduction are words like 'must', 'might', and 'can't' that help us say how sure we are about something in English.

When to use it

We use these modal verbs in English to talk about what we think is true or possible, based on the information we have. They help us show if we are sure, not sure, or think something is impossible.

Key forms

• must + base verb (e.g. must be)
• might/may/could + base verb (e.g. might be)
• can't + base verb (e.g. can't be)

Examples

Tips

• Don't use 'to' after these modal verbs. Say 'must be', not 'must to be'.
• Use the base form of the verb after the modal verb.
• Remember: 'must' is for things you are sure about, 'might/could/may' for possible things, and 'can't' for things you think are impossible.