Modal Verbs

1. Obligation

1.1. MUST Vinf

2. Prohibition

2.1. MUSTN'T Vinf

3. Lack of necessity

3.1. NEEDN'T V-inf = don't need to

3.2. NEEDN'T have Vpp >< didn't need to

4. Necessity

4.1. MUST V-inf >< HAVE to Vinf

5. Possibility

5.1. CAN Vinf (general possibility)

5.2. COULD/MAY/MIGHT Vinf (present/future possibility, in a specific situation)

5.3. COULD/MAY/MIGHT have Vpp (Past possibility)

6. Permission

6.1. COULD/MAY/MIGHT V-inf (asking permission-formal) >< CAN (informal)

6.2. MAY/ MAY NOT Vinf (giving /refusing permission- formal) >< CAN/CAN'T (informal)

7. logical deduction

7.1. Positive: MUST Vinf (present) >< MUST have Vpp (past)

7.2. Negative: CAN'T V-inf (present) >< CAN'T have Vpp (past)