a language user's knowledge of words
"After years of studying linguistics, she finally expanded her lexicon enough to understand every nuance in Shakespeare's sonnets."
a reference book containing an alphabetical list of words with information about them
"The professor told us to consult his personal lexicon before our final exam on obscure vocabulary."
The vocabulary of a language.
"The study of linguistics revealed that our digital lexicon has expanded rapidly to include countless new slang terms in just five years."
The word "lexicon" comes from the Greek lexikón, which originally meant a dictionary. It is derived from an earlier phrase meaning "a book of words," tracing back to roots related to speaking and gathering.