Modal verbs Part 5: Absence of Necessity & Prohibition

Hello, dear learners!

We have learnt a lot of useful rules about modal verbs in the previous lessons. You can revise them: Part 1, Part 2, Part 3, Part 4.

Today we are going to talk about negative forms of modal verbs for expressing absence of necessity and prohibition.

So, let's start!

Absence of Necessity  

We use needn't/ don't have to/ don't need to ; didn't need to; needn't have done for expressing the  absence of necessity.

• Needn't/ don't have to/ don't need to + present infinitive are used to show that  this action isn't necessary to do in the  present or in the  future :

 
You needn't/ don't have to/ don't need to translate this article. (It isn't necessary).

• Didn't need to do / didn't have to do are used to show that this action was not necessary to do in the past. These expression emphasise that an action didn't happen in the past because we knew that it wasn't necessary: 

He didn't need to / didn't have to translate this article. (It wasn't necessary, so he didn't do this).

• Needn't + bare perfect infinitive are used to show that the action was done in the past, even though it was not necessery.

He needn't have translated the article. Ann had already done this. (It wasn't necessary, but he done). 

Prohibition

 We use mustn't / can't to express that it is forbidden to do something / it is against the rules or law to do something.

You mustn't / can't park your car here.