Lycanthropy is the transformation of a person into the form of a wolf or to gain wolf-like characteristics. The word lycanthropy is sometimes used generically for any transformation of a human into animal form, though the precise term for that is technically “therianthropy”. Sometimes, “zoanthropy” is used instead of “therianthropy”. The word has also been linked to Lycaon, a king of Arcadia who, according to Ovid’s Metamorphoses, was turned into a ravenous wolf in retribution for attempting to serve human flesh (his own son) to visiting Zeus in an attempt to disprove the god’s divinity.

A more modern use of the word is in reference to a mental illness called lycanthropy in which a patient believes he or she is, or has transformed into, an animal and behaves accordingly. This is sometimes referred to as clinical lycanthropy to distinguish it from its use in legends.