Negation

Part of speech: noun (n.)

1. The act of denying; assertion of the nonreality or untruthfulness of anything; declaration that something is not, or has not been, or will not be; denial; -- the opposite of Ant: affirmation. Our assertions and negations should be yea and nay. Rogers.

2. Description or definition by denial, exclusion, or exception; statement of what a thing is not, or has not, from which may be inferred what it is or has.