Modal/ Semi-modal

1. We use modal verbs to modify the meaning of the main verb.

1.1. Can/could

1.1.1. Ability, permission, request, advice

1.2. Will / Shall

1.2.1. Future/ willingness/ promises and offers/ conditional sentences

1.3. May/ might/ could

1.3.1. Possibility/ permission

1.4. Would/ would have

1.4.1. Requests/ past of will/ conditional sentences/ habits

1.5. Must/ mustn't

1.5.1. Rules/ obligation

1.6. Should/ shouldn't

1.6.1. Recommendation/ advice

1.7. Should have/ shouldn't have

1.7.1. Regret/ criticism

1.8. Needn't/ needn't have

1.8.1. Lack of obligation

1.9. May be/ might be/ must be/ can't + be/ +be -ing form

1.9.1. Speculation about the present

1.10. May have/ might have/ must have/ can't have+past participle/ +been -ing form

1.10.1. Speculation about past

1.11. Could have/ couldn't have

1.11.1. Possibility in the past/ critisism

1.12. Will have

1.12.1. Future completion

2. Semi-modal verbs have some of the characteristics of modals, but not all.

2.1. Have to/ had to/ have got to

2.1.1. Rules/ obligation

2.2. Don't have to/ didn't have to

2.2.1. Lack of obligation

2.3. Ought to

2.3.1. Obligation/ advise

2.4. Need to

2.4.1. Necessity/ instructions/ guidance

2.5. Don't need to/ didn't need to

2.5.1. Lack of obligation

2.6. Would like/ would like to

2.6.1. Offers/ invitations/preferences

2.7. Be able to

2.7.1. Ability/ infinitive of can