Modal Verbs

1. Ability

1.1. Can

1.2. Be able to

2. Prohibition

2.1. Mustn't

3. Obligation

3.1. Must

3.2. Have to

4. Advice

4.1. Should

4.2. Shouldn't

4.3. Ought to

5. Posibility

5.1. Could

5.2. May

5.3. Might

6. Permission

6.1. Be allowed to

6.2. Can

6.3. May

7. Absence of Obligation

7.1. Don't have to

7.2. Needn't

8. Necesity

8.1. Need

8.2. Needn't

9. Deduction

9.1. 99% Sure

9.1.1. Must

9.1.2. Can't

9.2. 50% Sure

9.2.1. Possibility

9.2.2. May

9.2.3. Possibility

9.3. Possibility

9.3.1. Could

9.3.2. Might