| Form | Example | |
|---|---|---|
| Three systems | epistemic (likely) · deontic (obliged) · dynamic (able) | She must be tired. (I deduce) |
| Modal adverbs | certainty scale: certainly → presumably → arguably | He can't be home — his car's gone. |
| Formal patterns | it may be argued / it would be advisable / one might suppose | It might rain. (probability) |
| Past modals | must/can't/should/would/could/might have + PP | You must apologise. (I require) |