vocabulary

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun All the words of a language.
• noun The sum of words used by, understood by, or at the command of a particular person or group.
• noun A list of words and often phrases, usually arranged alphabetically and defined or translated; a lexicon or glossary.
• noun A supply of expressive means; a repertoire of communication.

from The Century Dictionary.

• noun A list or collection of the words of a language, a dialect, a single work or author, a nomenclature, or the like, arranged usually in alphabetical order and briefly defined and explained; a glossary; a word-book; a dictionary or lexicon: as, a vocabulary of Anglo-Indian words; a vocabulary of technical terms; a vocabulary of Virgil.
• noun The words of a language; the sum or stock of words employed in a language, or by a particular person; range of language.
• noun Synonyms Vocabulary, Dictionary, Glossary, Lexicon, Nomenclature. A vocabulary, in the present use, is a list of words occurring in a specific work or author, generally arranged alphabetically, concisely defined, and appended to the text; whereas we generally apply the term dictionary to a word-book of all the words in a language or in any department of art or science, without reference to any particular work: thus, we speak of a vocabulary to Cæsar, but of a dictionary of the Latin language, or of architecture, chemistry, etc. An exception to this may be where the words of an author are so fully treated, by derivation, illustration, etc., as to seem to amount to more than a vocabulary: as, a Homeric dictionary. A glossary is yet more restricted than a vocabulary, being a list and explanation of such terms in a work or author as are peculiar, as by being technical, dialectal, or antiquated: as, a glossary to Chaucer, Burns, etc; a glossary of terms of art, philosophy, etc. Lexicon was originally and is often still confined to dictionaries of the Greek or Hebrew tongues, but it is also freely applied to a dictionary of any dead or merely foreign language: as, a German-English lexicon. A nomenclature is a complete list of the names or technical terms belonging to any one division or subdivision of science.
• noun Idiom, Diction, etc. See language.

from the GNU version of the Collaborative International Dictionary of English.

• noun A list or collection of words arranged in alphabetical order and explained; a dictionary or lexicon, either of a whole language, a single work or author, a branch of science, or the like; a word-book.
• noun A sum or stock of words employed.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A usually alphabetized and explained collection of words e.g. of a particular field, or prepared for a specific purpose, often for learning.
• noun The collection of words a person knows and uses.
• noun The stock of words used in a particular field.
• noun The words of a language collectively.
• noun A range of artistic or stylistic forms or techniques

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a language user's knowledge of words
• noun the system of techniques or symbols serving as a means of expression (as in arts or crafts)
• noun a listing of the words used in some enterprise