Need is a semi-modal verb because in some ways it is like a modal verb and in other ways like a main verb.

We use need mostly in the negative form to indicate that there is no obligation or necessity to do something:

You needn’t take off your shoes.

Affirmatives with the semi-modal need are not common and they are used in formal contexts. There is almost always a negative word (e.g. no one, nobody, nothing) or phrase in the clause, even if the verb phrase is affirmative:

No one need think that we are doing this every week. (we are not doing this every week)

Nobody need know the name of the person who made the complaint.

Not a thing need change on this page.

Need comes first in the verb phrase (after the subject and before another verb):

Let’s forget about it. No one need know about it.

We can’t use another modal verb with need:

No one need read this.

Not: No one need must read this. or No one must need read this.

We form the negative by adding not after need. Need not can be contracted to needn’t. We don’t use don’t/doesn’t/didn’t with the semi-modal verb need:

You need not spend a lot of money on presents. (formal) (or You needn’t spend a lot of money on presents.)

Not: You don’t need spend a lot of money on presents.

See also:

Modal verbs

Semi-modal need and main verb need

The question form of the semi-modal need is not very common. It is rather formal. The subject and need change position to form questions. We don’t use do/does/did.

Need we write this down?

Not: Do we need write this down?

The semi-modal need is most common in the negative. We use it to show that there is no obligation:

We needn’t spend much time on this topic. It’s not going to be in the exam.

Cans of soup needn’t be kept in the fridge.

The semi-modal need has no past simple form. Instead, we use didn’t need to or didn’t have to when we express no obligation in the past:

I didn’t need to buy any books. They were all in the library. (main verb need + to)

(or I didn’t have to buy any books. They were all in the library.)

Not: I didn’t need buy any books. They were all in the library.

See also:

Semi-modal need and main verb need

We use needn’t have + -ed form to refer to events which happened but which the speaker considers were unnecessary:

You needn’t have waited for me. (You waited for me but it wasn’t necessary.)

You needn’t have bought so much food. There are only three of us staying for the weekend. (You bought a lot of food but it wasn’t necessary.)

We can use main verb need as an alternative to semi-modal need. Main verb need is followed by to and it changes with person, number and tense (I, you, we, they need to; she, he, it needs to; I, you, she, he, it, we, they needed to).

Semi-modal need

Main verb need

Comment

Need it be so dark in here? (formal)

Does it need to be so dark in here?

In these examples, the meaning is the same for semi-modal need and main verb need + to.

You needn’t mention this to your father.

You don’t need to mention this to your father.

We must use the main verb need when it is followed by a noun phrase or -ing clause:

You don’t need [noun phrase]an umbrella.

Not: You needn’t an umbrella.

My hair doesn’t need [-ing clause]cutting for at least another month.

Not: My hair needn’t cutting for at least another month.

The main verb need is followed by to when used with another verb.

I need to have my hair cut.

Not: I need have my hair cut.