Learner's definition of VOCABULARY
1 [count] : the words that make up a language 2 : all of the words known and used by a person
— sometimes used in an exaggerated way to make a forceful statement
He has a large/wide vocabulary. [=he knows and uses many words]
He has a somewhat limited vocabulary.
Reading helped to expand/improve her vocabulary.
Our passive vocabulary [=the words we understand] is larger than our active vocabulary. [=the words we use ourselves]
3 [count, noncount] : words that are related to a particular subject 4 [count, noncount] : a set of forms or elements that are used for expression in an art, in music, etc.