Refers to the total set of words known or used by a person, group, or within a specific field. Often used in linguistic or academic contexts.
His lexicon is rich in technical terms.
Linguists study the development of children's lexicon.
Specifically a reference work listing words, especially for ancient languages like Greek, Latin, or Hebrew. Less commonly used for modern dictionaries.
I consult a lexicon of classical Greek.
This lexicon explains Hebrew words in detail.