Definition of nonius in US English:

nonius

noun

  • A device consisting of a series of concentric arcs engraved on a quadrant, used for the accurate measurement of angles, altitudes, and heights. Also (in full "nonius quadrant"): the quadrant itself; also called pantometer. Frequently attributive Now chiefly historical.

Origin

Mid 18th century; earliest use found in Philosophical Transactions of the Royal Society of London. From post-classical Latin Nonius, Latinized form of the name of Pedro Nunes, Portuguese mathematician, who invented this device and described it in his work De Crepusculis.

Pronunciation

nonius

/ˈnəʊnɪəs/