lexicon

[ lek-si-kon, -kuhn ]
/ ˈlɛk sɪˌkɒn, -kən /

noun, plural lex·i·ca [lek-si-kuh] /ˈlɛk sɪ kə/, lex·i·cons.

a wordbook or dictionary, especially of Greek, Latin, or Hebrew.
the vocabulary of a particular language, field, social class, person, etc.
inventory or record: unparalleled in the lexicon of human relations.
Linguistics.
  1. the total inventory of morphemes in a given language.
  2. the inventory of base morphemes plus their combinations with derivational morphemes.

Origin of lexicon

1595–1605; < Medieval Latin < Medieval Greek, Greek lexikón, noun use of neuter of lexikós of words, equivalent to léx(is) speech, word (see lexis) + -ikos -ic
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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British Dictionary definitions for lexicon

lexicon
/ (ˈlɛksɪkən) /

noun

a dictionary, esp one of an ancient language such as Greek or Hebrew
a list of terms relating to a particular subject
the vocabulary of a language or of an individual
linguistics the set of all the morphemes of a language

Word Origin for lexicon

C17: New Latin, from Greek lexikon, n use of lexikos relating to words, from Greek lexis word, from legein to speak
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012