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1. a period of time equal to 3600 seconds; 1/24th of a calendar day
2. Astronomy an angular measurement of right ascension equal to 15° or a 24th part of the celestial equator
1. A unit of time equal to 60 minutes, i.e. 1/24 of a day.
2. A unit of angle equal to 15° of arc, i.e. 1/24 of a circle. See right ascension.
A unit of time equal to 3600 seconds. Abbreviated h; hr.