An Etymological Dictionary of Astronomy and Astrophysics

The 24th part of a day; 60 minutes.
An angular unit of right ascension, equivalent to 15°.

Etymology (EN): Hour, from M.E. houre, from O.Fr. hore, from L. hora “hour, time, season,” from Gk. hora “any limited time,” used of day, hour, season, year; cognate E. → year.

Etymology (PE): Sâ’at, from Ar.