hour

—hourless, adj.

/oweur, ow"euhr/, n.

1. a period of time equal to one twenty-fourth of a mean solar or civil day and equivalent to 60 minutes: He slept for an hour.

2. any specific one of these 24 periods, usually reckoned in two series of 12, one series from midnight to noon and the second from noon to midnight, but sometimes reckoned in one series of 24, from midnight to midnight: He slept for the hour between 2 and 3 A.M. The hour for the bombardment was between 1300 and 1400.

3. any specific time of day; the time indicated by a timepiece: What is the hour?

4. a short or limited period of time: He savored his hour of glory.

5. a particular or appointed time: What was the hour of death? At what hour do you open?

6. a customary or usual time: When is your dinner hour?

7. the present time: the man of the hour.

8. hours,

a. time spent in an office, factory, or the like, or for work, study, etc.: The doctor's hours were from 10 to 4. What an employee does after hours is his or her own business.

b. customary time of going to bed and getting up: to keep late hours.

c. (in the Christian church) the seven stated times of the day for prayer and devotion.

d. the offices or services prescribed for these times.

e. a book containing them.

9. distance normally covered in an hour's traveling: We live about an hour from the city.

10. Astron. a unit of measure of right ascension representing 15°, or the twenty-fourth part of a great circle.

11. a single period, as of class instruction or therapeutic consultation, usually lasting from 40 to 55 minutes. Cf. clock-hour.

12. Educ. Also called credit hour. one unit of academic credit, usually representing attendance at one scheduled period of instruction per week throughout a semester, quarter, or term.

13. the Hours, Class. Myth. the Horae.

14. one's hour,

a. Also, one's last hour. the instant of death: The sick man knew that his hour had come.

b. any crucial moment.

adj.

15. of, pertaining to, or noting an hour.

[1175-1225; ME (h)oure < AF; OF (h)ore < L hora < Gk hóra time, season]

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▪ unit of time

      in timekeeping, 3,600 seconds, now defined in terms of radiation emitted from atoms of the element cesium under specified conditions. The hour was formerly defined as the 24th part of a mean solar day—i.e., of the average period of rotation of the Earth relative to the Sun. The hour of sidereal time, ¹/₂₄ of the Earth's rotation period relative to the stars, was about 10 seconds shorter than the hour of mean solar time.

      In even earlier systems of timekeeping, an hour was ¹/₁₂ of a period of daylight or darkness—hence, variable in length with seasonal changes in the length of day and night. The custom of dividing the cycle of day and night into 24 periods seems to have originated with the ancient (Egypt, ancient) Egyptians.

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