| A | B |
| Indicates no choice at all | must |
| Moral obligation; there is choice, but one is better | should |
| Strong moral obligation, coercion or warning | had better |
| Indicates a possible course of action; a suggestion | could |
| Places the verb in the conditional | would |
| Indicates absence of obligation | negative of have to (ex.-don't have to) |
| Indicates possiblility | may |
| Indicates capability | can |
| Asks for or grants permission | may |
| Asks for or grants permission (colloquial) | can |
| Indicates past capability | could |
| Indicates no choice at all | have got to |
| Indicates no choice at all | have to |
| Moral obligation; there is choice, but one is better | ought to |
| Indicates possiblility | might |