What is Lexical diversity?

Lexical diversity is one aspect of 'lexical richness' and refers to the ratio of different unique word stems to the total number of words. The term is used in applied linguistics and is quantitatively calculated using numerous different measures including Text-Type Ratio , vocd, and the measure of textual lexical diversity.

A common problem with lexical diversity measures, especially TTR, is that text samples containing large number of tokens give lower values for TTR since it is often necessary for the writer or speaker to re-use several function words. One consequence of this is that lexical diversity is better used for comparing texts of equal length. Newer measures of lexical diversity attempt to account for sensitivity to text length.