Negation

Webster's Dictionary of the English Language

·adv 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.

II. Negation ·adv 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 affirmation.