vigesimal

vigesimal (vai-JES-uh-muhl) - adj., of, relating to, proceeding by, occurring in intervals of, or based on the number 20.


So counting by twenties, grouping by twenties, or number systems using base 20 (such as in Mayan and Tlingit). The term is from Latin vīgēsimus, variant of vīcēsimus, twentieth.


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---L.