Negates the meaning of the modified verb.
Did you take out the trash? No, I did not.
To no degree.
It's not you, it's me.
(understatement, litotes) Used to modify superlatives to indicate the opposite or near opposite, often in a form of understatement.
It was not my favorite movie of all time.
And not.
He painted the car blue and black, not solid purple.
(1990s) Used to indicate that the previous phrase was meant sarcastically or ironically.
I really like hanging out with my little brother watching Barney... not!