To express lack of necessity (also called absence of obligation), speakers usually use "don't have to", don't need to", "needn't" .
The form that we use to express lack of necessity could be one of the following:
- He doesn't have to get up early.
- He doesn't need to get up early.
- He needn't get up early
Expressing lack of necessity in the present:
I don't have to take my umbrella. It isn't raining need I needn't take my umbrella. It isn't raining
- I don't have to drive fast.
- I don't need to write the report myself. My secretary can do that for me.
- I needn't buy all these things.
- It isn't necessary to take your umbrella. It isn't raining.
Expressing lack of necessity in the past:
I didn't have to take my raincoat. It wasn't raining need I needn't have taken my raincoat
- I didn't have to tell him about my project. He already knew everything about it.
Expressing lack of necessity in the future:
I won't have to take my jacket. It won't be cold. need
- I won't have to call on my grandfather tomorrow morning. He'll be at the doctor's for his regular medical check up.
1."Lack of necessity" is also called "absence of obligation".
2. "Needn't" is followed by an infinitive without "to".
Example: " I needn't buy tomatoes".
3. - In the past there is a difference in the negative forms of need:
- didn't need = didn't have to
I didn't need to wait, she was just on time.
(She was on time. I didn't have to wait.)
- needn't = absence of obligation/lack of necessity
We needn't have waited, they didn't come.
(It was useless to wait. They didn't come)
A student is asking the teacher about his homework:
Teacher: You don't have to write a long essay; a short one would be ok! Student: What about the grammar exercise do we need to revise the lesson before we can do it? Teacher: No, you needn't do the exercise at home as we will surely do it together in the next English lesson. Student: Ok! Good bye sir. Teacher: Good bye!