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Related to sidereal month: synodic month, lunar eclipse
The average period of revolution of the moon around the earth in reference to a fixed star, equal to 27 days, 7 hours, 43 minutes in units of mean solar time.
(Astronomy) See month5
1. any of the 12 parts, as January or May, into which the calendar year is divided.
2. the time from any day of one calendar month to the corresponding day of the next.
3. a period of four weeks or 30 days.
a. Also called solar month. one-twelfth of a solar year.
5. months, an indefinitely long period of time: I haven't seen him for months.Idioms:
a month of Sundays, an indeterminately great length of time.
[before 900; Middle English; Old English mōnath; c. Old Frisian mōnath, Old High German mānōd, (German Monat), Old Norse mānathr, Gothic mēnōths. See moon]