Lewis & Short

nĕgātĭo, ōnis, f. [nego],

  1. I. a denying, denial, negation, Cic. Sull. 13, 39: negatio inficiatioque facti, id. Part. 29, 102.
  2. II. In partic., a word that denies, a negative, App. Dogm. Plat. 3, p. 32, 38.