Kendall rank correlation vs Kendall's tau

Kendall rank correlation and Kendall's tau both are nouns.

Word	Noun	Adjective	Verb	Adverb
Kendall rank correlation	Yes	No	No	No
Kendall's tau	Yes	No	No	No

As nouns, Kendall rank correlation and Kendall's tau are synonyms defined as:

Kendall rank correlation and Kendall's tau: a nonparametric measure of the agreement between two rankings

Other synonyms of Kendall rank correlation include tau coefficient of correlation.

Kendall rank correlation (noun)	Kendall's tau (noun)
a nonparametric measure of the agreement between two rankings	a nonparametric measure of the agreement between two rankings