Vocabulary refers to the collection of words a particular person, group of people, socioeconomic group, profession, and so on, knows and uses. The technical term for vocabulary is lexis.
The active vocabulary is all the words used expressively (in writing, speaking or signing) and the passive vocabulary is all the words recognized and understood, although not necessarily used expressively. An adult’s passive vocabulary is about one third larger than their active vocabulary (Crystal, 2006)