Nonius definition

Latinised form of the name of Pedro Nuñes (1502-78), a Portuguese mathematician and geographer.

a device for adjusting the accuracy of mathematical instruments, later superseded by the vernier
- 1997: 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 — Thomas Pynchon Mason & Dixon