When to use don't and doesn't in a sentence?

Answer 1

Doesn't or Don't?

Doesn't, does not, or does is used with the third person singular--words like he, she, and it.

Don't, do not, or do is used for other subjects.

EXAMPLES">EXAMPLES

Incorrect: It don't matter anymore.

Correct: It doesn't matter anymore.

Incorrect: Grandfather don't see too well.

Correct: Grandfather doesn't see too well.

Correct: His glasses don't help him much.

Answer 2

Use "don't" when the subject is plural or the pronouns "I" or "you." Use "doesn't" when the subject is singular (like he, she, it) to denote the negative form of "do" or "does" in a sentence. For example, "I don't like coffee" or "She doesn't eat meat."