negate

/nɪˈɡeɪt/
verb
  1. To cancel out the effect or force of something; to make something ineffective.
    • The new evidence negates the earlier theory about the crime.
    • Adding more sugar will negate the sour taste of the lemon.
    • A good defense can negate the opponent's strongest attack.
  2. To deny or contradict a statement or idea.
    • He negated her claim by showing the receipts.
    • The study negates the popular belief that coffee is bad for you.
    • The witness negated the suspect's alibi with clear proof.
  3. In logic or mathematics, to make a statement or value negative or opposite.
    • The programmer used a function to negate the boolean value.
    • To negate a number, you change its sign from positive to negative.
    • In logic, to negate a true statement makes it false.