A list or collection of words or of words and phrases usually alphabetically arranged and explained or defined.
For many people, the word vocabulary is primarily associated with the number of words that a person knows; one either has a large or a small vocabulary. But the word has many shades of meaning and is nicely representative of the nuanced and multi-hued nature of so much of the English lexicon.
Vocabulary may indeed refer to the collection of words known by an individual or by a large group of people. It may also signify the body of specialized terms in a field of study or activity (“the vocabulary of science”). It may designate a physical object, such as a book, in which a collection of (usually alphabetized) words is defined or explained. And it may name things other than words, such as “a list or collection of terms or codes available for use,” “a set or list of nonverbal symbols” (such as marine alphabet flag signals), and “a set of expressive forms used in an art” (as in “the vocabulary of dance”).