When should I use don't and when should I use doesn't? — Learners Everywhere
Many users have written to us asking whether don't or doesn’t is correct in a particular sentence, or asking what the difference between don't and doesn’t is.
Both don’t and doesn’t are contractions using the verb do and the word not. It's easier to see which one is the correct choice if you expand the contractions: don’t is a contraction of "do not" and doesn't is a contraction of "does not." We know that a verb with a third person singular subject gets an -s or -es on the end in the simple present tense. This is true for all regular verbs.
The verb call has an -s when it has a third person singular subject:
you (all) call
The verb miss has an -es when it has a third person singular subject:
you (all) miss
With a third person singular subject, the verb do becomes does:
you (all) do
So then, in the contractions with the word not, don't becomes doesn't with a third person singular subject:
I don't [=I do not]
we don't [=we do not]
you don't [=you do not]
you (all) don't [=you (all) do not]
he/she/it doesn't [=he/she/it does not]
they don't [=they do not]
I hope this helps. For more posts about words and usage, like us on Facebook and follow us on Twitter!