pronoun+be not
I am not hungry.
I'm not hungry.
They are not friendly.
They're not friendly.
That dog is not friendly.
That dog isn't friendly.
It is not raining today.
It isn't raining today.
She is not my sister.
She's not my sister.
He is not thirsty.
He's not thirsty.
She is not my sister.
She isn't my sister.
Carlos and Betty are not married.
Carlos and Betty aren't married.
He is not my brother.
He's not my brother.
She is not my cousin.
She's not my cousin.
He is not my brother.
He isn't my brother.
The teacher is not in the library.
The teacher isn't in the library.
They are not friends.
They're not friends.
We are not sick.
We're not sick.
They are not friends.
They aren't friends.
We are not sad.
We aren't sad.
We are not late.
We're not late.
She is not tired.
She's not tired.
We are not late.
We aren't late.
She is not tired.
She isn't tired.