Hour

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The hour (common symbol: h or hr; also known as a stound) is a unit of time. It is not an SI unit but is accepted for use with the SI with the symbol h.[1]

Contents

Definition

In modern usage, an hour is a unit of measurement of time of the duration of 60 minutes, or 3,600 seconds. It is 1/24 of a median Earth day. An hour in the Universal Coordinated Time (UTC) time standard can include a negative or positive leap second, and may therefore have a duration of 3599 or 3601seconds for adjustment purposes.

Etymology

Middle English ure first appears in the 13th century, as a loanword from Old French ure, ore, from Latin hora, ultimately from Greek ὥρα "season, time of day, hour". Middle English ure, Anglo-French houre replaced Old English tīd (which survives as Modern English tide) and stund (which survives as stound — compare Old High German stunta, from a Germanic *stundō "time, interval, while").

Greek ὥρα is cognate to English year, both from a PIE *i̯ēro- "year, summer".

History

The hour was originally defined in ancient civilizations (including those of Egypt,[2] Sumer, India, and China) as either one twelfth of the time between sunrise and sunset or one twenty-fourth of a full day[citation needed].[dubious ]

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