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Correct Uses of Need and Needn't

Need is used to express necessity or obligation to do something, generally in an interrogative tone.

The negative form needn’t (or need not) is also used to express necessity or obligation; but in the negative sense—i.e., absence of necessity or obligation to do something.

Consider the following expressions:

  • Need I come again? (meaning: Is it necessary for me to come again?)
  • You needn’t do it now. (meaning: It isn’t necessary for you to do it now.)

Ways of Using Need

We can use need either as an ordinary verb or as a modal verbOpens in new window (followed by a bare infinitiveOpens in new window).

  1. Using Need as an Ordinary Verb

    Need can be used, as an ordinary verb, with do, does, did. Note that we may also use have to instead of need. Survey the example sentences below:

    • Do I need to go so soon? (or do I have to go ...)
    • He doesn’t need to go to the bank. (or He doesn't have to go ...)
    • I didn’t need to buy the book. (or I didn't have to buy ...)
  2. Using Need as a Modal Verb

    When need is used as a modal verbOpens in new window, it is most usually used in negative sentencesOpens in new window and it doesn’t change its tenseOpens in new window and doesn’t add ‘-s’ for the third person singular. Survey the following examples:

    • I’ve already cleaned the car so you needn’t bother to do it.
    • We needn’t go till about ten o’clock.
    • Andy needn’t go to the doctor today.
    • I was very nervous before the interview, but I needn’t have worried—I got the job!
    Important Hint!  

    Note that we may use don’t have to (or haven’t got to) instead of needn’t, but needn’t is more common.

    1. Using Need in Expressions

      In other styles of formal written English need is used in this way with negative words such as hardly, never, nobody / no one, and only. Survey the following expressions:

      • The changes need only be small to make the proposals acceptable. (less formally → The changes only need to be …)
      • Nobody ever need know about the money. (less formally Nobody ever needs to know …)
      • I don’t want my parents to know. They need never find out. (less formally They never need to find out.)
    2. Expressing Necessity

      We use need to express when something is necessary or when we are obligated to do something, as shown below:

      • We need to gather a few points to progress to the next round.
      • The top rim needs to be cut off.
      • We need to invest more in tourism.
      • The animals need water to survive the drought.
    3. Expressing Lack of Necessity

      We may use either needn’t or don’t have to with slight difference in meaning to say that it is unnecessary to do something. Survey the following examples:

      • You needn’t cut the grass, I’ll do it later.
        → (or You don’t need to cut the grass …)
      • He needn’t apologize, it wasn’t his fault.
        → (or He doesn’t need to apologize …)
      • They needn’t stay.
        → (or They don’t need to …)
      • You needn’t whisper. Nobody can hear us.
        → (or You don’t have to …)

      Important Hint!  

      Note that some people prefer needn’t when it is the speaker who decides the lack of necessity, and don’t have to when somebody else or external rules make something unnecessary. Compare the following:

      • As you worked late yesterday you needn’t come in until ten tomorrow morning. (based on the speaker’s decision); and:
      • We’ve been told that we don’t have to be at work until ten tomorrow. (based on reported speech of someone else’s decision.)

      Note also that we sometimes use needn’t (or don’t have to) to say that something is not necessarily true. However, we don’t use mustn’t in this way. Survey the following expressions.

      • Volcanoes needn’t erupt constantly to be classified as ‘active’.
        → (or Volcanoes don’t have to erupt …[NOT Volcanoes mustn’t erupt ..])
      • Nowadays it needn’t cost a fortune to own an e-book reader.
        → (or Nowadays it doesn’t have to cost … [NOT Nowadays it mustn’t cost …)

Emphasis on Needn't (Need not)

The negative forms needn’t and need not are used to express necessity or obligation in the negative sense. Particularly, need not, is mostly used in the present tenseOpens in new window to express negative sense. Ponder the following example sentences.

  • You need not wait for him.
  • He need not (NOT needs not) worry about the money.

Likewise, needn't is used in this structure needn’t + have + past participle to express a past necessity or obligation in the negative sense. See examples below.

  • She needn’t have abused her position.
  • You needn’t have picked a quarrel with him.

Needn’t + Perfect Infinitive

This is a structure used to express an unnecessary action which was nevertheless performed. Survey the following expressions.

  • I needn’t have written to him because he phoned me shortly afterwards. (but I had written, thus wasting my time)
  • He needn’t have left home at 6.00pm as the train doesn’t start till 7.00pm. (so he will have an hour to wait)
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