Negation in grammar refers to the process of making a statement or sentence negative. It is typically done by using words like "not," "never," "no," or "nothing" to indicate the opposite of an affirmative statement.
Negation involves turning a positive statement into a negative one. For example: Positive: She is happy. Negative: She is not happy.
The word "not" is used to negate the verb "is" in this case.