Bad faith (Latin: mala fides) is a sustained form of deception which consists of entertaining or pretending to entertain one set of feelings while acting as if influenced by another. It is associated with hypocrisy, breach of contract, affectation, and lip service. It is not to be confused with heresy (supposedly false religious faith). It may involve intentional deceit of others, or self-deception.
Some examples of bad faith include: Soldiers waving a white flag and then firing when their enemy approaches to take prisoners (cf. perfidy); a company representative who negotiates with union workers while having no intent of compromising; a prosecutor who argues a legal position that he knows to be false; an insurer who uses language and reasoning which are deliberately misleading in order to deny a claim.