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Millennium
A period of 1,000 years. By extension, a thousand-year anniversary. In the Western calendar, the third millennium is marked beginning midnight, 1 January 2001. |
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Minute
A period of time defined as 60 seconds. The term is derived from the Latin pars minuta, a "small part", indicating a division of the unit of hour. |
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MJD
Abbreviation for Modified Julian Day, a version of the Julian Day number system which produces a smaller working number by subtracting the Julian Day number of the epoch, 17 November 1858 (JD# 2,400,000.5), from the Julian Day number of a date. The fraction corrects the start of MJD to midnight, not noon. |
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Month, anomalistic
The period required for the Moon to complete one circuit of its orbit, using the perigee as the reference point. |
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Month, draconic
The period required for the Moon to complete one circuit of its orbit, using the ascending node as the reference point. |
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Month, nodal
See month, draconic. |
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Month, sidereal
The period required for the Moon to complete one circuit of its orbit, using a fixed star as the reference point. |
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Month, synodic
The period required for the Moon to complete one circuit of its orbit, using the Sun as the reference point. |
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Movable
In the context of "feast", the term means a day observed by a rule that causes the day to fall on different dates in different years. The most important movable feasts in the ecclesiastical calendar are Easter, Pentecost, and Lent. |
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NM
Abbreviation for New Moon. |
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Node
The point on the celestial sphere where the great circle representing the orbit of a body intersects the great circle representing the plane of the ecliptic of the same body. The point where an orbiting body moves from below the ecliptic plane to above it is the ascending node, whereas the other is the descending node. |
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Nona
A watch in the medieval monastery system beginning at the ninth hour, or midafternoon. The term noon is derived from this word. |
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