Definition of "vigesimal" []

• Twentieth. (adjective)
• Proceeding or occurring in intervals of 20. (adjective)
• Based on or relating to 20. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "America, are always thought of and alluded to as vigesimal scales."
• "Hence these and similar number systems, though commonly alluded to as vigesimal, are really mixed scales, with 20 as their primary base."
• "In a perfect vigesimal numeric system, third order should contain 400 days (20 x 20 x 1); but at this point Maya priests introduced a variant for calendar computation purposes."