lex ‧ i ‧ con /ˈleksɪkən $ -kɑːn, -kən/ BrE AmE noun
[ Date: 1600-1700 ; Language: Late Greek ; Origin: lexikon , from lexikos 'of words' , from Greek lexis 'word, speech' , from legein 'to say' ]
1 . the lexicon technical all the words and phrases used in a language or that a particular person knows
2 . [countable] an alphabetical list of words with their meanings, especially on a particular subject or in a particular language:
a lexicon of geographical terms