A vigesimal numeral system has a base of twenty.
Twenty (vingt) is used as a base number in French. E.g. quatre-vingt means 4 times 20, i.e. 80.
Twenty (tyve) is used as a base number in the Danish language: Tres (short for tresindstyve) means 3 times 20, i.e. 60; firs (short for firsindstyve) means 4 times 20 i.e. 80. halvtreds means (3 - 1/2) times 20, i.e. 50; halvfjerds means (4 - 1/2) times 20, i.e. 70; and halvfems means (5 - 1/2) times 20, i.e. 90.
Twenty (ugain) is used as a base number in the Welsh language, although in the latter part of the twentieth century a decimal counting system came to be preferred, with the vigesimal system becoming 'traditional'. Deugain means 2 times 20 i.e. 40, trigain means 3 times 20 i.e. 60. Prior to the currency decimalisation in 1971, papur chwigain (6 times 20 paper) was the nickname for the 10 shilling (=120 pence) note.
In English, counting by the score has been used historically, as in the famous opening of the Gettysburg Address "Four score and seven years ago...", meaning eighty-seven years ago. This usage has fallen into disuse in modern times, however.