can, cannot, can't

The modal auxiliary can and the negative forms cannot, can't

The auxialiary/modal can has the same form regardless the subject. There is no -s in the 3rd person singular.

The auxialiary/modal can is used with a main verb in its infinitive. It can be used alone in short answers.

There is no contracted form of can in affirmative sentences.

Affirmative sentences Negative sentences
long form contracted form long form contracted form
I can sing. --- I cannot sing. I can't sing.
You can sing. --- You cannot sing. You can't sing.
He can sing. --- He cannot sing. He can't sing.
She can sing. --- She cannot sing. She can't sing.
It can sing. --- It cannot sing. It can't sing.
We can sing. --- We cannot sing. We can't sing.
You can sing. --- You cannot sing. You can't sing.
They can sing. --- They cannot sing. They can't sing.