mendacity
The fact or condition of being untruthful; dishonesty.
uncountable
[…] Treating the assertion of the witness as the effect, he [Pierre-Simon Laplace] considers as its two possible causes, the veracity or mendacity of the witness on the particular occasion, that is, the truth or falsity of the fact.
A deceit, falsehood, or lie.
countable
The scandalous bronze-lacker age, of hungry animalisms, spiritual impotencies and mendacities, will have to run its course, till the Pit swallow it.
Where it comes from
From Late Latin mendacitas, from Latin mendāx (“deceitful, deceptive, lying”) + -itās (suffix forming nouns indicating a state of being). Mendāx is derived from mentior (“to deceive, lie”) (from mēns, mentis (“mind; intellect; judgment, reasoning”), from Proto-Indo-European *méntis (“thought”)) + -āx (suffix forming adjectives expressing a tendency or inclination), or from Proto-Indo-European *mend- (“to fault”). By surface analysis, Latin mendāc- + -ity.
Adapted from the Wiktionary entry mendacity (CC BY-SA 4.0).