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month

  (mŭnth) pronunciation
n.
  1. A unit of time corresponding approximately to one cycle of the moon's phases, or about 30 days or 4 weeks.
  2. (Abbr. mo.) One of the 12 divisions of a year as determined by a calendar, especially the Gregorian calendar. Also called calendar month.
  3. A period extending from a date in one calendar month to the corresponding date in the following month.
  4. A sidereal month.
  5. A lunar month.
  6. A solar month.
idiom:

month of Sundays Informal.

  1. An indefinitely long period of time: It will take you a month of Sundays to chop all that wood.

[Middle English moneth, from Old English mōnath.]

USAGE NOTE   The singular month, preceded by a number and a hyphen, is used as a compound attributive: a three-month vacation. The plural possessive form without a hyphen is also possible: a three months' vacation.


 
 

Any of several units of time based on the revolution of the Moon around Earth.

The calendar month is one of the 12 arbitrary periods into which the calendar year is divided. See also Calendar.

The synodic month, the period of the lunar phases, is the average period of revolution of the Moon with respect to the Sun, the same as the average interval between successive full moons. Its duration is 29.531 days. See also Phase (astronomy).

The tropical month is the period required for the mean longitude of the Moon to increase 360°, or 27.322 days.

The sidereal month, 7 s longer than the tropical month, is the average period of revolution of the Moon with respect to a fixed direction in space.

The anomalistic month, 27.555 days in duration, is the average interval between closest approaches of the Moon to Earth. The variation in the Moon's distance from the Earth causes a variation in the apparent size of the Moon and thus in the duration of solar eclipses.

The nodical month, 27.212 days in duration, is the average interval between successive northward passages of the Moon across the ecliptic, points known as nodes. Since eclipses can occur only when the Sun and Moon are near such nodes, this period is also known as a draconic month, after the Chinese mythical dragon that supposedly ate the Sun to cause a solar eclipse. See also Eclipse; Moon.


 
Idioms: month

Idioms beginning with month:
month of Sundays, a

In addition to the idiom beginning with month, also see by the day (month); (for months) on end.


 

[Etymology: Moon] time Any of the various periods associated with the passage of the Moon about Earth, and hence of roughly 30 days. As discussed under time, there are various lengths of month. The obvious natural month is the time between successive full moons or other lunar phase-point. Because of the ellipticity of the orbits of Earth and of the Moon, the length of such a period varies slightly. The mean value, approximately 29.5 (mean solar) days, is termed the synodic month (also lunation). Since Earth is simultaneously travelling about the Sun, with the same anti-clockwise turning viewed from the (North) Pole Star as the Moon's orbiting and thereby changing the relative position of the illuminating Sun, the synodic month is greater than the sidereal month, the time for one orbit relative to the stars, by about one twelfth of that value. Other close but distinct periods defined are the tropical month, being the time for the mean position to increase 360° (effectively one lap around Earth); the draconic or nodical month, being the period between northward crossings of the ecliptic, which is shortened by the marked regressive gyration of the lunar orbital plane; and the anomalistic month, the period between successive perigees (closest approaches). The values of these various months (in mean solar days) at the opening of the year 2002 were
[The Astronomical Almanac for the Year 2002 (Washington: US Government Printing Office and London: HMSO, 2001), also Explanatory Supplement to the Astronomical Almanac (Mill Valley, CA: University Science Books, 1994).]

1 synodic month= 29.530 589~ days= 29 days12 h44 min2.9~ s
1 sidereal month= 27.321 662~ days= 27 days7 h43 min11.6~ s
1 tropical month= 27.321 582~ days= 27 days7 h43 min4.7~ s
1 anomalistic month= 27.554 550~ days= 27 days13 h18 min33.4~ s
1 draconic month= 27.212 221~ days= 27 days5 h5 min35.9~ s


Despite our visual perception being close to 30 days, the common understanding and hence the vernacular lunar month has 28 days; this gives a month of 4 whole weeks, but misleads people widely concerning the incidence of the full moon, etc. The average calendar month of the familiar Gregorian calendar, which has about 30.4 days, is closer to the visible month than the vernacular lunar one. The variation of the Gregorian calendar month, from 28 to 31 days, is well known; being greater on average than the synodic month means that one or two months each year contain two new moons, while February can have no new moon. Similarly, the seasons contain three but can contain four full moons. The term ‘blue moon’ applies to the penultimate full moon in a season with four (though it is often applied to the more frequent second in a month).The human menstrual [Lat: ‘month’] period, sometimes believed to be in phase with the Moon, ranges roughly from 20 to 40 days.

(It appears that the lunar month was about 30.5 days, with 13.1 such months in a solar year of about 400 days, a billion years ago.)

See calendar for a discussion of months relative to years.

See lune for a special division of the synodic month.

 
in chronology, the conventional period of a lunation, i.e., passage of the moon through all its phases. It is usually computed at approximately 29 or 30 days. For the computation of the month and its harmony with the solar calendar and for the months in others than the Gregorian calendar, see calendar. For the difference between the sidereal month and the synodic month, see moon. Certain stones have in ancient and modern times been connected with the months; these lucky stones, or birthstones, are often given as follows: January [from the god Janus]: garnet; February [Lat.,=expiatory, because of ancient rites]: amethyst; March [from the god Mars]: bloodstone or aquamarine; April: diamond; May: agate or emerald; June [from the gens Junius]: pearl or moonstone; July [from Julius Caesar]: ruby or onyx; August [from Augustus]: carnelian or peridot; September [Lat.,= seven; formerly the 7th month]: chrysolite or sapphire; October [eight]: beryl, tourmaline or opal; November [nine]: topaz; December [ten]: turquoise or zircon.


 
Word Tutor: month
pronunciation

IN BRIEF: One of the twelve divisions of the calendar year.

pronunciation Some people stay longer in an hour than others do in a month. — William Howells

 
Wikipedia: month

The month is a unit of time, used with calendars, which is approximately as extensive as some natural period related to the motion of the Moon. The traditional concept arose with the cycle of moon phases; such months (lunations) are synodic months and last approximately 29.53 days. From excavated tally sticks, researchers have deduced that people counted days in relation to the Moon's phases as early as the Paleolithic age. Synodic months are still the basis of many calendars today.

Astronomical background

The motion of the Moon in its orbit is very complicated and its period is not constant. Moreover, many cultures (most notably those using the ancient Hebrew (Jewish) calendar and the Islamic calendar) start a month with the first appearance of the thin crescent of the new moon after sunset over the western horizon. The date and time of this actual observation depends on the exact geographical longitude as well as latitude, atmospheric conditions, the visual acuity of the observers, etc. Therefore the beginning and lengths of months in these calendars can not be accurately predicted. Most Jews currently follow a precalculated calendar, but the Karaites rely on actual moon observations.

Sidereal month

The period of the Moon's orbit as defined with respect to the celestial sphere is known as a sidereal month because it is the time it takes the Moon to return to a given position among the stars (Latin: sidus): 27.321661 days (27 d 7 h 43 min 11.5 s). This type of month has been observed among cultures in the Middle East, India, and China in the following way: they divided the sky into 27 or 28 lunar mansions, defined by asterisms (apparent groups of stars), one for each day of the sidereal month.

Tropical month

It is customary to specify positions of celestial bodies with respect to the vernal equinox. Because of precession, this point moves back slowly along the ecliptic. Therefore it takes the Moon less time to return to an ecliptic longitude of zero than to the same point amidst the fixed stars: 27.321582 days (27 d 7 h 43 min 4.7 s). This slightly shorter period is known as tropical month; cf. the analogous tropical year of the Sun.

Anomalistic month

Like all orbits, the Moon's orbit is an ellipse rather than a circle. However, the orientation (as well as the shape) of this orbit is not fixed. In particular, the position of the extreme points (the line of the apsides: perigee and apogee), makes a full circle (lunar precession) in about nine years. It takes the Moon longer to return to the same apsis because it moved ahead during one revolution. This longer period is called the anomalistic month, and has an average length of 27.554551 days (27 d 13 h 18 min 33.2 s). The apparent diameter of the Moon varies with this period, and therefore this type has some relevance for the prediction of eclipses (see Saros), whose extent, duration, and appearance (whether total or annular) depend on the exact apparent diameter of the Moon. The apparent diameter of the full moon varies with the full moon cycle which is the beat period of the synodic and anomalistic month, and also the period after which the apsides point to the Sun again.

Draconic month

Also called the nodical month. The orbit of the moon lies in a plane that is tilted with respect to the plane of the ecliptic: it has an inclination of about five degrees. The line of intersection of these planes defines two points on the celestial sphere: the ascending node, when the moon's path crosses the ecliptic as the moon moves into the northern hemisphere, and descending node when the moon's path crosses the ecliptic as the moon moves into the southern hemisphere. The draconic or nodical month is the average interval between two successive transits of the moon through its ascending node. Due to the sun's gravitational pull on the moon, the moon's orbit gradually rotates westward on its axis, which means the nodes gradually rotate around the earth. As a result, the time it takes the moon to return to the same node is shorter than a sidereal month. It lasts about 27-1/5 days (27.212220 days or 27 d 5 h 5 min 35.8 s). The plane of the moon's orbit precesses over a full circle in about 18.6 years.

Because the moon's orbit is inclined with respect to the ecliptic, the sun, moon, and earth are in line only when the moon is at one of the nodes. Whenever this happens a solar or lunar eclipse is possible. The name "draconic" refers to a mythical dragon, said to live in the nodes and eat the sun or moon during an eclipse.

Synodic month

This is the average period of the Moon's revolution with respect to the sun. The synodic month is responsible for the moon phases because the Moon's appearance depends on the position of the Moon with respect to the Sun as seen from the Earth. While the moon is orbiting the earth, the Earth is progressing in its orbit around the Sun. This means that after completing a sidereal month the Moon must move a little farther to reach the new position of the Earth with respect to the Sun. This longer period is called the synodic month from the Greek syn hodô (σὺν ὁδῴ), meaning "with the way [of the sun]". Because of the perturbations of the orbits of the Earth and Moon, the actual time between lunations may range from about 29.27 to about 29.83 days. The long-term average duration is 29.530588 days (29 d 12 h 44 min 2.8 s). The synodic month is used in the Metonic cycle.

Month lengths

Here is a list of the average length of the various astronomical lunar months [1]. These are not constant, so a first-order (linear) approximation of the secular change is provided:

Valid for the epoch J2000.0 (1 Jan. 2000 12:00 TT):

sidereal month 27.321661547 + 0.000000001857 × y days
tropical month 27.321582241 + 0.000000001506 × y days
anomalistic month 27.554549878 − 0.000000010390 × y days
draconic month 27.212220817 + 0.000000003833 × y days
synodic month 29.530588853 + 0.000000002162 × y days

Note: time expressed in Ephemeris Time (more precisely Terrestrial Time) with days of 86,400 SI seconds. y is years since the epoch (2000), expressed in Julian years of 365.25 days. Note that for calendrical calculations, one would probably use days measured in the time scale of Universal Time, which follows the somewhat unpredictable rotation of the Earth, and progressively accumulates a difference with ephemeris time called ΔT.

Calendrical consequences

For more details on this topic, see lunar calendar and lunisolar calendar.

At the simplest level, all lunar calendars are based on the approximation that 2 lunations last 59 days: a 30 day full month followed by a 29 day hollow month — but this is only marginally accurate and quickly needs correction by using larger cycles, or the equivalent of leap days.

Second, the synodic month does not fit easily into the year, which makes constructing accurate, rule-based lunisolar calendars difficult. The most common solution to this problem is the Metonic cycle, which takes advantage of the fact that 235 lunations are approximately 19 tropical years (which add up to not quite 6940 days). However, a Metonic calendar (such as the Hebrew calendar) will drift against the seasons by about 1 day every 200 years.

The problems of creating reliable lunar calendars may explain why solar calendars, having months which no longer relate to the phase of the moon, and being based only on the motion of the sun against the sky, have generally replaced lunar calendars for civil use in most societies.

Months in various calendars

Julian and Gregorian calendars

The Gregorian calendar, like the Julian calendar before it, has twelve months:

  1. January, 31 days
  2. February, 28 days, 29 in leap years, or 30 on certain occasions in related calendars
  3. March, 31 days
  4. April, 30 days
  5. May, 31 days
  6. June, 30 days
  7. July, 31 days
  8. August, 31 days
  9. September, 30 days
  10. October, 31 days
  11. November, 30 days
  12. December, 31 days


One of Wikipedia's sister projects, Wiktionary, provides translations of each of the Gregorian/Julian calendar months into a dozen or more languages. Month-by-month links are provided here: January, February, March, April, May, June, July, August, September, October, November, December.

The average month in the Gregorian calendar has a length of 30.4167 days or 4.345 weeks in a non-leap year and 30.5 days or 4.357 weeks in a leap year.

Months existing in the Roman calendar in the past include:

The famous mnemonic Thirty days hath September is the most common way of teaching the lengths of the months in the English-speaking world.

On top of the knuckles (yellow): 31 daysBetween the knuckles (blue): 30 daysFebruary (red) has 28 or 29 days.
Enlarge
On top of the knuckles (yellow): 31 days
Between the knuckles (blue): 30 days
February (red) has 28 or 29 days.

The knuckles of the four fingers of one's hand and the spaces between them can be used to remember the lengths of the months. By making a fist, each month will be listed as one proceeds across the hand. All months landing on a knuckle are 31 days long and those landing between them are not. When the knuckle of the index finger is reached (July), go back to the first knuckle (or over to the first knuckle on the other fist, held next to the first) and continue with August. This physical mnemonic has been taught to primary school students for many decades.[2][3][4][5]

Calends, nones, and ides

The ides occur on the thirteenth day in eight of the months, but in March, May, July, and October, they occur on the fifteenth. The nones always occur 8 days before the ides, i.e., on the fifth or the seventh. The calends are always the first day of the month.

French Republican calendar

This calendar was proposed during the French Revolution, and used by the French government for about twelve years from late 1793. There were twelve months of 30 days each, grouped into three ten-day weeks called décades. The five or six extra days needed to approximate the tropical year were placed after the months at the end of each year. A period of four years ending on a leap day was to be called a Franciade. It began at the autumn equinox:

  • Autumn:
  1. Vendémiaire
  2. Brumaire
  3. Frimaire
  • Winter:
  1. Nivôse
  2. Pluviôse
  3. Ventôse
  • Spring:
  1. Germinal
  2. Floréal
  3. Prairial
  • Summer:
  1. Messidor
  2. Thermidor
  3. Fructidor

Islamic calendar

There are also twelve months in the Islamic calendar. They are named as follows:

  1. Muharram ul Haram (or shortened to Muharram) محرّم
  2. Safar صفر
  3. Rabi`-ul-Awwal (Rabi' I) ربيع الأول
  4. Rabi`-ul-Akhir (or Rabi` al-Tיhaany) (Rabi' II) ربيع الآخر أو ربيع الثاني
  5. Jumaada-ul-Awwal (Jumaada I) جمادى الأول
  6. Jumaada-ul-Akhir (or Jumaada al-THaany) (Jumaada II) جمادى الآخر أو جمادى الثاني
  7. Rajab رجب
  8. Sha'aban شعبان
  9. Ramadhan رمضان
  10. Shawwal شوّال
  11. Dhul Qadah (or Thw al-Qi`dah) ذو القعدة
  12. Dhul Hijja (or Thw al-Hijjah) ذو الحجة

Hebrew Calendar

The Hebrew calendar has 12 or 13 months.

  1. Nisan, 30 days ניסן
  2. Iyyar, 29 days אייר
  3. Sivan, 30 days סיון
  4. Tammuz, 29 days תמוז
  5. Av, 30 days אב
  6. Elul, 29 days אלול
  7. Tishri, 30 days תשרי
  8. Heshvan, 29/30 days חשון
  9. Kislev, 29/30 days כסלו
  10. Tevet, 29 days טבת
  11. Shevat, 30 days שבת
  12. Adar 1, 30 days, intercalary month אדר א
  13. Adar 2, 29 days אדר ב

Adar 1 is only added 7 times in 19 years. In ordinary years, Adar 2 is simply called Adar.

Hindu Calendar

The Hindu Calendar has various systems of naming the months. The months in the lunar calendar are:

  1. Chaitra
  2. Vaishaakha
  3. Jyaishtha
  4. Aashaadha
  5. Shraavana
  6. Bhaadrapada
  7. Aashvayuja
  8. Kaartika
  9. Maargashiirsha
  10. Pausha
  11. Maagha
  12. Phaalguna

These are also the names used in the Indian national calendar for the newly redefined months.

The names in the solar calendar are just the names of the zodiac sign in which the sun travels. They are

  1. Mesha
  2. Vrishabha
  3. Mithuna
  4. Kataka
  5. Simha
  6. Kanyaa
  7. Tulaa
  8. Vrishcika
  9. Dhanus
  10. Makara
  11. Kumbha
  12. Miina

Tamil calendar

  1. Chitirai
  2. Vaikasi
  3. Aani
  4. Aadi
  5. Aavani
  6. Purratasi
  7. Aiypasi
  8. Kaarthigai
  9. Maargazhi
  10. Thai
  11. Maasi
  12. Panguni

Iranian/Persian calendar

The Iranian / Persian calendar, currently used in Iran and Afghanistan, also has 12 months. The Persian names are included in the parentheses.

  1. Farvardin (فروردین)‎, 31 days
  2. Ordibehesht (اردیبهشت)‎, 31 days
  3. Khordad (خرداد)‎, 31 days
  4. Tir (تیر)‎, 31 days
  5. Mordad (مرداد)‎, 31 days
  6. Shahrivar (شهریور)‎, 31 days
  7. Mehr (مهر)‎, 30 days
  8. Aban (آبان)‎, 30 days
  9. Azar (آذر)‎, 30 days
  10. Dey (دی)‎, 30 days
  11. Bahman (بهمن)‎, 30 days
  12. Esfand (اسفند)‎, 29 days, 30 in leap years

Icelandic/Old Norse calendar

The old Icelandic calendar is not in official use anymore, but some holidays and annual feasts are still calculated according to it in Iceland. It has 12 months, broken down into two groups of six often termed "winter months" and "summer months". The calendar is peculiar in that the months always start on the same weekday rather than on the same date. Hence Þorri always starts on a Friday sometime between January 19 and January 25 (Old style: January 9 to January 15) , Góa always starts on a Sunday between February 18 and February 24 (Old style: February 8 to February 14).

  • Skammdegi ("Short days")
  1. Gormánuður (mid October - mid November, "slaughter month" or "Gór's month")
  2. Ýlir (mid November - mid December, "Yule month")
  3. Mörsugur (mid December - mid January, "fat sucking month")
  4. Þorri (mid January - mid February, "frozen snow month")
  5. Góa (mid February - mid March, "Góa's month, see Nór")
  6. Einmánuður (mid March - mid April, "lone" or "single month")
  • Náttleysi ("Nightless days")
  1. Harpa (mid April - mid May, Harpa is a female name, probably a forgotten goddess, first day of Harpa is celebrated as Sumardagurinn fyrsti - first day of summer)
  2. Skerpla (mid May - mid June, another forgotten goddess)
  3. Sólmánuður (mid June - mid July, "sun month")
  4. Heyannir (mid July - mid August, "hay business month")
  5. Tvímánuður (mid August - mid September, "two" or "second month")
  6. Haustmánuður (mid September - mid October, "autumn month")

Notes

  1. ^ Derived from ELP2000-85: M. Chapront-Touzé, J. Chapront (1991): Lunar tables and programs from 4000 B. C. to A. D. 8000. Willmann-Bell, Richmond VA; ISBN 0-943396-33-6
  2. ^ Days in each month
  3. ^ Happy New Year! Or is it? by Education World
  4. ^ Mnemonics to improve memory
  5. ^ The Boy Mechanic: A Handy Calendar (1913) from Project Gutenberg

See also


 
Translations: Translations for: Month

Dansk (Danish)
n. - måned

idioms:

  • a month of Sundays    i månedsvis, i evigheder, så langt som et ondt år

Nederlands (Dutch)
maand

Français (French)
n. - mois

idioms:

  • a month of Sundays    la semaine des quatre jeudis (fam), à la saint glinglin (fam)

Deutsch (German)
n. - Monat

idioms:

  • a month of Sundays    sehr lange Zeit

Ελληνική (Greek)
n. - μήνας (του έτους)

idioms:

  • a month of Sundays    του αγίου ποτέ

Italiano (Italian)
mese

idioms:

  • a month of Sundays    un'eternità

Português (Portuguese)
n. - mês (m)

idioms:

  • a month of Sundays    um período indefinidamente longo

Русский (Russian)
месяц, месячник

idioms:

  • a month of Sundays    долгий срок

Español (Spanish)
n. - mes

idioms:

  • a month of Sundays    nunca, ni por casualidad

Svenska (Swedish)
n. - månad

中文(简体) (Chinese (Simplified))

idioms:

  • a month of Sundays    很久

中文(繁體) (Chinese (Traditional))
n. - 月

idioms:

  • a month of Sundays    很久

한국어 (Korean)
n. - 월

idioms:

  • a month of Sundays    아주 오랫동안, 좀처럼 없는 기회

日本語 (Japanese)
n. - ひと月

idioms:

  • a month of Sundays    非常に長い間

العربيه (Arabic)
‏(الاسم) شهر ثلاثون يوما‏

עברית (Hebrew)
n. - ‮חודש‬


 
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American Sign Language
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Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
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Idioms. The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Company. All rights reserved.  Read more
Measures and Units. A Dictionary of Weights, Measures, and Units. Copyright © Donald Fenna 2002, 2004. All rights reserved.  Read more
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