nonagenary

From Latin nōnāgēnārius (“containing 90”) either directly or via Middle French nonagénaire, from Latin nōnāgēnī (“90 each”) + -ārius (“-ary”), from nōnāgintā (“nine tens, 90”).

nonagenary (not comparable)

1. (rare) Of or related to the number ninety.

   Coordinate terms: unary, binary, ternary, trinary, tetranary, quintenary, hexanary, septenary, octonary, nonary, decenary, vicenary, tricenary, quadragenary, quinquagenary, semicentenary, sexagenary, septuagenary, octogenary, centenary, millenary

nonagenary (plural nonagenaries)

1. (astronomy, astrology, obsolete) Synonym of square or quadrature: a rising at a 90 degree angle to the position of another heavenly body, particularly the sun.
   • 1601, Pliny, translated by Philemon Holland, The Historie of the World, volume I, page 10:

     As for Mars, as he is neerer to the Sunne, so feeleth he the Sunne beames by a quadrant aspect, to wit, ninetie degrees: wherupon that motion tooke the name, called the first and second Nonagenarie, from both risings.

• “† nonagenary, n.”, in OED Online ⁠, Oxford, Oxfordshire: Oxford University Press, 2021.