An Etymological Dictionary of Astronomy and Astrophysics

The quantity x in a fraction x/y). The quantity y is
the → denominator.

Etymology (EN): L.L. numerator “a counter, numberer,” from L. numera(re)
“to number,” → number + -tor a suffix forming personal agent nouns from verbs and, less commonly, from nouns.

Etymology (PE): Šomârân, agent noun of šomârdan, → number.