Rarely Used Modals in English Language.

Ought to

1. It is used to express moral obligation, and duty

Ex: you ought to obey your teachers.

You oughtn't to behave like this 

The idea of obligation can also be expressed with should or must. However ought to is used when a feeling of duty is involved.

2. Ought to + perfect infinitive (have + V3) expresses an obligation not fulfilled in the past or something desirable not done in the past:

Example, 

You ought to have obeyed your parents. (it means which was desirable from your side but you did not do.)

4. Oughtn't + perfect infinitive ( have+ v3) expresses the idea that something wrong or undesirable was done in the past.

Example

You oughtn't to have involved in the fight. ( but you did).

Ought to, like Should, can be used to express a deduction or assumption about present and future action.

He ought to pass this year.

As ought to verbally sound unacceptable, so we prefer either should or must.

Need. 

1.When need is used as main verb not an auxiliary modal, Need means require/be in the need of. So need + noun/pronoun or need + infinitive is used to express one's requirements:

Example

I need your help in this.

He needs job.

2. The negative and interrogative of need is formed with do.

I don't need your help.

Does he need job?

3. Need to can be used to express obligation or necessity:

You need to work hard to score good marks.

Need is not much used in the affirmative.so must/have to is used instead.

He need not to work hard.

Needn't take V1 instead of full infinitive.

Examples

You need to go to school daily.

You needn't go to school daily.

Note: Need not is always used as plural form. Needs not is wrong.

Example

He needn't work hard.

4. The past tense forms of need not are:

A) hadn't got to

He had not got to shave himself.

B) didn't have to

He didn't have to shave himself.

C) didn't need to

He didn't need to shave himself.

General response to Need is must.

Need I take Ram with me?

Yes, you must.

5. Need not + perfect infinitive (have+ V3) expresses the  idea that an action which was neither necessary nor obligatory was performed in the past.

Example

Ram needn't have left Sita. ( but he did)

Note:

A) didn't have to/did not need to indicates that there was no obligation  and so the action was not performed:

Example

He didn't have to go Delhi. ( And he didn't go)

B) Needn't+ perfect infinitive indicates that although there was no obligation or necessity an action was performed in the past:

Example

He needn't have gone to Delhi. ( However, he went to Delhi.)

Dare

1.Dare as main verb means 'to challenge'.In such sentences we use dare + object + infinitive (with to). In such sentences dare has a singular form (dares) with singular subject and plural form (dare) with plural subject.

Example

He dares me to visit the haunted house at night.

2.Dare as modal auxiliary means 'be bold enough to'/'to have the courage'. it is commonly used in interrogative and negative sentences.

How dare you challenge me?

As a modal it (dare) is always in plural form.

She/they daren't oppose me.

3. The past form of dare not is daren't + V1.

Example

He daren't drive without licence.