of a person is defined either as the set of all words
that are understood by that person or the set of all words likely to be used by that person when constructing new sentences
Tests of vocabulary are integral components of intellectual assessment within psychology. Level of vocabulary has been consistently found to predict overall level of intellectual functioning as well as educational achievement.
It is widely circulated that the English language
has the largest vocabulary of any language, but this claim is difficult to formulate precisely, and essentially impossible to prove.