An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Characterized by light of one color or by radiation of a single wavelength or narrow range of wavelengths.

→ mono-; → chromatic.

The sum of → absorption coefficient (κ_ν) and → scattering coefficient (σ_ν) at a given frequency: k_ν = κ_ν + σ_ν. See also the → Rosseland mean opacity.

→ monochromatic; → opacity.

1) A single algebraic term, such as 2xy, 125, 2x². The → degree of the monomial is the sum of the exponents of all included variables. Constants have the monomial degree of 0.
2) Of, pertaining to, or consisting of a monomial.

→ mono- + nomial, short for → nomnial.

A → morphismf : Y → X if, for any two morphisms u,v : Z → Y, f u = f v  implies that u =v.

→ mono-; → morphism.

The fact of having only a single meaning. Same as → univocity. Compare with → polysemy.

From → mono- "single," + sem, from sema "sign," → semantic, + -y.

Takcemi, from tak-, → mono-, + cem, → meaning, + noun suffix -i.

The belief or doctrine that there is only one → God.

→ mono-; → theism.

Of a mathematical function, either continuously increasing or decreasing.

From Fr. monotone, from Gk. monotonos "monotonous, of one tone," from monos, → mono- "single, alone" + tonos "tone" + → -ic.

Yeknavâxt "monotonous," from yek "one, single," + navâxt"rhythm," from navâxtan, navâzidan "to play an instrument; to gratify," navâ "music, song, melody;" Mid.Pers. nw'c "to treat kindly, honour," niwag "music, melody;" Proto-Iranian *ni-uac-, from *ni- (→ ni-) + *uac- "to speak, treat kindly," → word.

A seasonal change in wind direction bringing dry air or heavy rain in India and nearby lands.

Monsoon, from Du. monssoen, from Port. monçao, from Ar. mausim "season." It was first applied to the winds over the Arabian Sea, which blow for six months from northeast and for six months from southwest, but it has been extended to similar winds in other parts of the world.

Bâd, → "wind;" mowsem, related to mowsem, from Ar. mausim, as above.

A computer-intensive technique that relies on repeated random sampling of a statistical population to compute its results. Monte Carlo simulation is often used for approximate numerical computations when application of strict methods requires too much calculation, or when it is infeasible or impossible to compute an exact result with a deterministic algorithm.

The term Monte Carlo was coined in the 1940s by physicists (Stanislaw Ulam, Enrico Fermi, John von Neumann, and Nicholas Metropolis) working on nuclear weapon projects in the Los Alamos National Laboratory. The name is a reference to a famous casino in Monaco which, it is said that, Ulam's uncle would borrow money to gamble at. → method.

A period of time based on the revolution of the Moon around the Earth. Several types of months are defined: → anomalistic month; → draconic month; → sidereal month; → synodic month; → tropical month.

O.E. monað, from P.Gmc. *mænoth- (O.N. manaðr, M.Du. manet, Du. maand, O.H.G. manod, Ger. Monat, Goth. menoþs "month"), related to *mænon-, → moon.

Mâh and mâng in Pers. are variants of the same term, the dominant form being mâh, while mâng (Av. from, see below) is used in classical literature as well as in some dialects: Tabari, Kurd. mâng, Laki, Tâti, Taeši mong, Šahmirzâdi, Sangesari mung; Mid.Pers. mâh "moon, month;" O.Pers. māha- "moon, month;" Av. māh- "month, moon," also māwngh-; cf. Skt. mās- "moon, month;" Gk. mene "moon," men "month;" L. mensis "month;" O.C.S. meseci, Lith. menesis "moon, month;" O.Ir. mi, Welsh mis, Bret. miz "month;" O.E. mona; E. moon, month; Ger. Mond, Monat; Du. maan; PIE base *me(n)ses- "moon, month."

Note: In Persian the same term, mâh, is used for two different, but related, concepts: moon and month. This was also the case for other IE languages, as shows the above etymology. However, other IE languages have evolved toward more accuracy by using different forms of the same initial term, as in E. moon / month or Ger. Mond / Monat. The Latin family uses two unrelated words, as in Fr. lune "moon" / mois "month" and Sp. luna / mes. An additional difficulty in present Pers. is that the adj. mâhi not only means "lunar" and "monthly" it also denotes "fish." For the sake of clarity and precision, this dictionary uses mângi for "lunar."

1) Natural satellite of the Earth. Mass 7.35 x 10²⁵ g = 1/81 or 0.0123 Earth's. Mean radius 1740 km = ~ 1/4 the Earth's; this relatively small size ratio makes the Earth-Moon system unique in the → solar system. Mean density 3.34 g cm^-3. Mean distance from Earth 384,400 km. → Escape velocity 2.38 km s^-1. → Surface gravity 162.2 cm s^-2 = 0.165 Earth's. → Sidereal period 27d 7h 43m 11s. → Eccentricity 0.0549. → Inclination of → orbital plane to → ecliptic 5° 8' 43''. → Obliquity 6° 41'. → Synodic period 29d 12h 44m 2s.9. → Orbital velocity 1.02 km s^-1. The Moon's average visual → Albedo is 0.12, a factor of three smaller than that of Earth. The Moon's → center of mass is displaced about 2 km in the direction of Earth. The average temperature on the surface of the Moon during the day is 107 °C. During the night, the average temperature drops to -153 °C. Studies of lunar rock have shown that melting and separation must have begun at least 4.5 x 10⁹ years ago, so the → crust of the Moon was beginning to form a very short time after the → solar system itself. Thickness of crust ~ 60 km; of mantle ~ 1000 km. Temperature of core ~ 1500 K. It would have taken only 10⁷ years to slow the Moon's rotation into its present lock with its → orbital period. Because of this → synchronous rotation, the Moon revolves once on its axis each time it orbits the Earth, thus always presenting the same face, the nearside, toward Earth. The Moon may have formed during a collision between the early Earth and a Mars-sized rocky planet about 4.6 billion years ago; → Theia.
2) A large body orbiting a planet.

O.E. mona, from P.Gmc. *mænon- (cf. O.S., O.H.G. mano, O.Fris. mona, O.N. mani, Du. maan, Ger. Mond, Goth. mena "moon"), cognate with Pers. mâh, as below, from PIE *me(n)ses- "moon, month."

Mâh and mâng in Pers. are variants of the same term, the dominant form being mâh, while mâng (Av. from, see below) is used in classical literature as well as in some dialects: Tabari, Kurd. mâng, Laki, Tâti, Taelši mong, Šahmirzâdi, Sangesari mung; Mid.Pers. mâh "moon, month;" O.Pers. māha- "moon, month;" Av. māh- "month, moon," also māwngh-; cf. Skt. mās- "moon, month;" Gk. mene "moon," men "month;" L. mensis "month;" O.C.S. meseci, Lith. menesis "moon, month;" O.Ir. mi, Welsh mis, Bret. miz "month;" O.E. mona; E. moon, month; Ger. Mond, Monat; Du. maan; PIE base *me(n)ses- "moon, month."

Note: In Persian the same term, mâh, is used for two different, but related, concepts: moon and month. This was also the case for other IE languages, as shows the above etymology. However, other IE languages have evolved toward more accuracy by using different forms of the same initial term, as in E. moon / month or Ger. Mond / Monat. The Latin family uses two unrelated words, as in Fr. lune "moon" / mois "month" and Sp. luna / mes. An additional difficulty in present Pers. is that the adj. mâhi not only means "lunar" and "monthly" it also denotes "fish." For the sake of clarity and precision, this dictionary uses mângi for "lunar."

Any of several theories about how the → Moon originated, among which: → fission theory, → capture theory, → co-formation theory, and → giant impact hypothesis. The model that is best supported by all the available data is the giant impact hypothesis. See also → canonical model.

→ lunar; → formation.

Same as → lunar halo.

→ Moon; → halo.

1) The number of days that have elapsed since the last → conjunction of the Sun and Moon. It is 7 days at → first quarter, 15 days at → full moon, and 22 days at → third quarter.
2) The time past since the → formation of the Moon.

→ Moon; → age.

1) Kohan-ruzi literally "age in days," from kohan-ruz "old in days," from kohan "old, ancient," kohné "worn;" Mid.Pers. kahwan "old, aged, worn;" pir; Mid.Pers. pir "old, aged, ancient;" Av. parô (adv.) "before, before (of time)," in front (of space); cf. Skt. puáh, combining form of puras "before (of time and place), in front, in advance;" mâh, → Moon.
2) Senn, → age.

The → rotation of the Moon's → orbit within the → orbital plane, whereby the axes of the ellipse change direction. The Moon's → major axis makes one complete revolution every 8.85 Earth years, or 3,232.6054 days, as it rotates slowly in the same direction as the Moon itself (direct, or → prograde motion). The Moon's apsidal precession is a → relativistic effect, and should not be confused with its → axial procession.

→ Moon; → apsidal; → precession.

The line connecting the Moon's north pole with its south pole, and passing through the center of the lunar disk. The longitude of the Moon's prime meridian is zero degrees.

→ Moon; → prime meridian.

A rainbow that arises from the refraction and reflection of moonlight on rain drops or mist.

→ moon; → bow.

A very small natural or artificial satellite orbiting a planet. Saturn has dozens of moonlets often associated with its → planetary rings.

→ moon; → -let.

Local disturbances in the ring structure caused by the gravitational influence of embedded satellites. If the satellite (moonlet) is large enough to clear a gap in the rings, the moonlet wakes become edge waves that precede the satellite on the inner edge and trail the satellite on the outer edge. For smaller satellites, the "gap-less" wakes have been nicknamed propellors (Ellis et al., 2007, Planetary Ring Systems, Springer).

→ moonlet; → wake.

The light of the Moon.

From → moon + → light.

Mahtâb (Gilaki mângtâb) from mah, mâh (mâng), → moon, + tâb "light," from tâbidan, tâftan "to shine," tafsidan "to become hot" (Av. tāp-, taf- "to warm up, heat," tafsat "became hot," tāpaiieiti "to create warmth;" cf. Skt. tap- "to spoil, injure, damage; to suffer; to heat, be/become hot," tapati "burns;" L. tepere "to be warm," tepidus "warm;" PIE base *tep- "warm").