An epithet (, ), also byname, is a descriptive term (word or phrase) known for accompanying or occurring in place of a name and having entered common usage. It has various shades of meaning when applied to seemingly real or fictitious people, divinities, objects, and binomial nomenclature. It can also be a descriptive title: for example, Pallas Athena, Phoebus Apollo, Alfred the Great, Suleiman the Magnificent, and Władysław I the Elbow-high. Many English monarchs have traditional epithets: some of the best known are Edward the Confessor, William the Conqueror, Richard the Lionheart, Æthelred the Unready, John Lackland and Bloody Mary.
The word epithet can also refer to an abusive, defamatory, or derogatory phrase. This use as a euphemism is criticized by Martin Manser and other proponents of linguistic prescription. H. W. Fowler complained that "epithet is suffering a vulgarization that is giving it an abusive imputation."
Epithets are sometimes attached to a person's name or appear in place of their name, as what might be described as a glorified nickname or sobriquet, and for this reason some linguists have argued that they should be considered as pronouns. It has also been argued that epithets are a phenomenon with the syntax-semantics interface, because they have components of both, and also a pragmatic dimension.
An epithet is linked to its noun by long-established usage. Not every adjective is an epithet. An epithet is especially recognizable when its function is largely decorative, such as if "cloud-gathering Zeus" is employed other than in reference to conjuring up a storm. "The epithets are decorative insofar as they are neither essential to the immediate context nor modeled especially for it. Among other things, they are extremely helpful to fill out a half-verse", Walter Burkert has noted.
Some epithets are known by the Latin term epitheton necessarium, as they are required to distinguish the bearers, as an alternative to numbers after a prince's name—such as Richard the Lionheart (Richard I of England), or Charles the Fat alongside Charles the Bald.