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The Collaborative International Dictionary of English v.0.48 (gcide)

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.
[1913 Webster]

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.
[1913 Webster]

{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.
[1913 Webster]


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.
[1913 Webster]

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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