noun, plural lex·i·ca [lek-si-kuh] Show IPA , lex·i·cons. 1. a wordbook or dictionary, especially of Greek, Latin, or hebrew. 2. the vocabulary of a particular language, field, social class, person, etc. 3. inventory or record: unparalleled in the lexicon of human relations. 4. Linguistics . a. the total inventory of morphemes in a given language. b. the inventory of base morphemes plus their combinations with derivational morphemes.