nonius

Borrowed from Latin Nonius, the Latinised form of the name of its inventor, Pedro Nunes (1502-78), a Portuguese mathematician and geographer.

• IPA^(key): /ˈnəʊnɪəs/
• Rhymes: -əʊniəs

nonius (plural noniuses)

1. A device for adjusting the accuracy of mathematical instruments, later superseded by the vernier.
   • 1997, Thomas Pynchon, Mason & Dixon, New York: Henry Holt and Company, →ISBN, →OCLC, page 332:

     Well, of course, one must manipulate the various Screw-Settings precisely, read the Nonius, and an hundred other details besides I’d but bore you with,—

• nonius horopter

• UNISON, Unions, unions, unison