Lexica

[lek-si-kon, -kuh n] /ˈlɛk sɪˌkɒn, -kən/

noun, plural lexica
[lek-si-kuh] /ˈlɛk sɪ kə/ (Show IPA), lexicons.
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.

/ˈlɛksɪkən/
noun
1.
a dictionary, esp one of an ancient language such as Greek or Hebrew
2.
a list of terms relating to a particular subject
3.
the vocabulary of a language or of an individual
4.
(linguistics) the set of all the morphemes of a language
noun

repertoire; compendium
Word Origin

Greek lexis ‘word, phrase’
n.

c.1600, “a dictionary,” from Middle French lexicon or directly from Modern Latin lexicon, from Greek lexikon (biblion) “word (book),” from neuter of lexikos “pertaining to words,” from lexis “word,” from legein “say” (see lecture (n.)).

Used originally of dictionaries of Greek, Syriac, Hebrew and Arabic, because these typically were in Latin and in Modern Latin lexicon, not dictionarius, was the preferred word. The modern sense of “vocabulary proper to some sphere of activity” (1640s) is a figurative extension.