a. [f. L. vīgēsimus, var. of vīcēsim-us: see VICESIMAL a.] Of or pertaining to twenty; based on the number twenty.
1656. Blount, Glossogr., Vigesimal, pertaining to the twentieth in number.
1727. Bailey (vol. II.).
1827. F. A. Walter, trans. Niebuhr’s Rom. Hist., I. 215. The ancient Azteks … calculated a great year of one hundred and four solar years. This they divided according to the Quinal and Vigesimal scale.
1871. Darwin, Desc. Man, I. v. 182. When we speak of three score and ten, we are counting by the vigesimal system.
1881. Tylor, Anthropol., xiii. (1904), 312. The vigesimal counting (by twenties) which is the regular mode in many languages.
