Mendaciously is derived from the Latin mendacium, meaning deceit or falsehood. It is frequently used to describe someone or something who is deceptive in their words or actions. mendacity can be used as a noun or a verb, and typically refers to the act of being deceptive. Mendacity can be simple, such as when someone lies to make themselves look better, or it can be more complicated, such as when a person uses deceptive tactics to try and mislead someone else. Mendacity can also be used to describe a situation in which someone is unwilling to admit they were wrong or to change their behavior.