- the linguistic form from which another form is historically derived, as the Latin cor “heart,” which is the etymon of English cordial, or the Indo-European *ḱ(e)rd-, which is the etymon of Latin cor, Greek kardía, Russian serdtse, and English heart.
- a form of a word or morpheme, usually the earliest recorded form or a reconstructed form, from which another word or morpheme is derived: the etymon of English "ewe" is Indo-European " * owi"
