doesn't , dozen

Doesn't or doesn't ( duh zent ) is a contraction ( short, informal form ) of "does not"--the third person singular ( he, she, it ) form of "do not"--
He doesn't want to stay for dinner.
It doesn't look like rain.

Dozen or dozen ( duh zen ) means twelve (12) of something--
Make sure to buy a dozen eggs at the store.
Could I have a dozen rolls please?

Now that you know that, you can say--
"One doughnut doesn't make a dozen."

Note--not to be confused with "don't", a contraction of "do not".
"Does", "does not" and "doesn't" go with he, she, or it--
He doesn't like that. He does not like that.
She doesn't like that. She does not like that.
"Do", "do not", and "don't" go with I, we, they, and you--
I don't like that. I do not like that.
We don't like that. We do not like that.
They don't like that. They do not like that.
You don't like that. You do not like that.