napier's bones

English Thesaurus

1. a set of graduated rods formerly used to do multiplication and division by a method invented by John Napier (noun.artifact)

hypernym	:	calculating machine, calculator,
definition	:	a small machine that is used for mathematical calculations (noun.artifact)

domain usage	:	plural, plural form,
definition	:	the form of a word that is used to denote more than one (noun.communication)