Etymology is the study of the history of words, their origins, and how their form and meaning have changed over time. By extension, the term "the etymology (of a word)" means the origin of the particular word.

For a language with a long written history, etymologists make use of texts in these languages and texts about the languages to gather knowledge about how words were used during earlier periods of their history and when they entered the languages in question. Etymologists also apply the methods of comparative linguistics to reconstruct information about languages that are too old for any direct information to be available.