vocabulary

A vocabulary is a set of words: either all the words of a language or the words that one person knows and can use.

A person's vocabulary has two sides. The receptive side holds the words understood when heard or read. The productive side holds the words a person can call up and use correctly in speech or writing. The receptive side is usually the larger of the two. Knowing a word is also a matter of degree. Full knowledge covers its sound, its spelling, its meaning, its grammatical role, the words it tends to appear with and the settings where it fits. Most words are learned gradually, through repeated meetings in reading, conversation and teaching, and a vocabulary can keep growing across a lifetime.

Vocabulary matters because it limits what a person can understand. A reader who does not know enough of the words on a page cannot follow its argument, and the size of a reader's vocabulary is closely tied to reading comprehension. A learner of a second language faces the same limit in every conversation. A wider vocabulary also helps in writing and speaking, because a precise word carries a distinction that a vague one blurs.