Sidereal \Si*de"re*al\, a. [L. sidereus, from sidus, sideris, a
constellation, a star. Cf. Sideral, Consider, Desire.]
1. Relating to the stars; starry; astral; as, sidereal
astronomy.
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2. (Astron.) Measuring by the apparent motion of the stars;
designated, marked out, or accompanied, by a return to the
same position in respect to the stars; as, the sidereal
revolution of a planet; a sidereal day.
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Sidereal clock, day, month, year. See under Clock,
Day, etc.
Sideral time, time as reckoned by sideral days, or, taking
the sidereal day as the unit, the time elapsed since a
transit of the vernal equinox, reckoned in parts of a
sidereal day. This is, strictly, apparent sidereal time,
mean sidereal time being reckoned from the transit, not of
the true, but of the mean, equinoctial point.
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Month \Month\ (m[u^]nth), n. [OE. month, moneth, AS.
m[=o]n[eth], m[=o]na[eth]; akin to m[=o]na moon, and to D.
maand month, G. monat, OHG. m[=a]n[=o]d, Icel. m[=a]nu[eth]r,
m[=a]na[eth]r, Goth. m[=e]n[=o][thorn]s. [root]272. See
Moon.]
One of the twelve portions into which the year is divided;
the twelfth part of a year, corresponding nearly to the
length of a synodic revolution of the moon, -- whence the
name. In popular use, a period of four weeks is often called
a month.
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Note: In the common law, a month is a lunar month, or
twenty-eight days, unless otherwise expressed.
--Blackstone. In the United States the rule of the
common law is generally changed, and a month is
declared to mean a calendar month. --Cooley's
Blackstone.
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A month mind.
(a) A strong or abnormal desire. [Obs.] --Shak.
(b) A celebration made in remembrance of a deceased person a
month after death. --Strype.
Calendar months, the months as adjusted in the common or
Gregorian calendar; April, June, September, and November,
containing 30 days, and the rest 31, except February,
which, in common years, has 28, and in leap years 29.
Lunar month, the period of one revolution of the moon,
particularly a synodical revolution; but several kinds are
distinguished, as the synodical month, or period from
one new moon to the next, in mean length 29 d. 12 h. 44 m.
2.87 s.; the nodical month, or time of revolution from
one node to the same again, in length 27 d. 5 h. 5 m. 36
s.; the sidereal, or time of revolution from a star to
the same again, equal to 27 d. 7 h. 43 m. 11.5 s.; the
anomalistic, or time of revolution from perigee to
perigee again, in length 27 d. 13 h. 18 m. 37.4 s.; and
the tropical, or time of passing from any point of the
ecliptic to the same again, equal to 27 d. 7 h. 43 m. 4.7
s.
Solar month, the time in which the sun passes through one
sign of the zodiac, in mean length 30 d. 10 h. 29 m. 4.1
s.
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