To have the courage to do something

I dare not go there.

I don’t dare (to) go there.

Dare we go yet?

Do we dare (to) go ?

We dare not go yet, dare we?

We don’t dare (to) go?

Verbs

Shades of obligation and necessity

Must

Obligation from the speaker’s viewpoint, e.g. I must do it (I consider it my duty or necessary that I should do it)

Have to

Obligation or necessity imposed by circumstances (circumstantial obligation), e.g. I have to do it (it is inevitable under the circumstances).

Be to

Obligation or necessity resulting from a previous arrangement or plan, e.g. We are to meet them at the theatre. = We arranged to them there.

Ought to

Should

Moral obligation, e.g. You ought to/ should help him if he is i trouble.

Need

Necessity, mostly absence of necessity, e.g. I need not = do not have to do it. I needn’t have done it.

Verbs

Shades of the meaning of supposition

May/might

Supposition implying uncertainty, e.g. He may/might be ill, I don’t really know.

Must (not used in the negative and with reference to the future)

Supposition bordering on assurance, high probability, e.g. He always comes at ten sharp. He must be there now.

Will/would (not used in the negative, not common)

Supposition bordering on assurance, e.g. You will have heard the news.

Should, ought to

Not used in the negative and not very common

Supposition bordering on assurance, e.g. According to the map this ought to/should be the way.

Verb

Form of the infinitive

Shades of the meaning

Examples

Could (subjunctive)

Perfect

Reproach for failing to do smth that was in one’s power

You could have worked harder and you would have finished it on time.

Might (subjunctive)

Non-perfect

Perfect

Reproach with a shade of sarcasm or annoyance on the part of the speaker

You really might do something for him.

You might have tried to persuade her.

Should

Ought

Perfect

Reproach for unfulfilled moral obligation or doing smth undesirable

She ought to have kept an eye on the child. You should have been more careful. You should not have squandered your money.