vocd

Etymology
. ‘vocd’ is the name of a computer program originally published in 2004 by Gerard McKee. The program calculates lexical diversity for use in psycholinguistic analysis, and the tool’s name is used somewhat interchangeably to describe the measure it provides.

Noun

 * 1)  A measure of the lexical diversity of a given corpus, determined by comparing the sizes of steadily larger random samples from the corpus against their respective type-token ratios.