We put not after the first word of the verb. In speaking, we often use the short form (n't).
I am not a thief.
They aren't coming.
It wasn't very cold there.
He is not a teacher.
Put the correct form of the verb do (Lesson 15) before not.
[A] He works on Fridays.
[N] He does not work on Saturdays.
[A] These shops sell food.
[N] They do not sell food.
[A] They arrived by bus.
[N] They didn't arrive by train.
Put not after the first auxiliary verb.
I haven't seen him for five years.
Our team has not been beaten this season.
He wouldn't have gone if he had known.
They aren't doing math this term.
Look at the different words in AFFIRMATIVE and NEGATIVE sentences.
[A] John is going somewhere but
[N] Maria isn't going anywhere.
[A] John has got some money but
[N] Maria hasn't got any money.
[A] They have got a lot of money but
[N] we haven't got much money.
[A] I've got a lot of friends but
[N] he hasn't got many friends.
[A] John and Maria have already left but
[N] we haven't left yet.
[A] John is leaving too and
[N] Maria isn't staying either.