a (linguistics) Either descended from the same attested source lexeme of ancestor language, or held on the grounds of the methods of historical linguistics to be regular reflexes of the unattested, reconstructed form of proto-language.
n One of a number of things allied in origin or nature.
n (legal|dated) One who is related to another on the female side.
n (legal|dated) One who is related to another, both having descended from a common ancestor through legal marriages.
n A word either descended from the same base word of the same ancestor language as the given word, or strongly believed to be a regularreflex of the same reconstructed root of proto-language as the given word.