falsity

1. The quality or condition of being false.
2. Something false; a lie.

noun

1. Betrayal, especially of a moral obligation: disloyalty, faithlessness, false-heartedness, falseness, infidelity, perfidiousness, perfidy, traitorousness, treacherousness, treachery, unfaithfulness. See continue/stop/pause, trust/distrust.
2. An erroneous or false idea: erroneousness, error, fallacy, falsehood, falseness, untruth. See correct/incorrect, true/false.
3. An untrue declaration: canard, cock-and-bull story, falsehood, fib, fiction, inveracity, lie², misrepresentation, misstatement, prevarication, story, tale, untruth. Informal fish story, tall tale. Slang whopper. See true/false.

Definition: dishonesty, deception
Antonyms: honesty, truth, truthfulness

The noun has 2 meanings:

Meaning #1: the state of being false or untrue
  Synonym: falseness
  Antonym: truth (meaning #2)

Meaning #2: a false statement
  Synonyms: falsehood, untruth, false statement