An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 368
nodal regression
  پسرفت ِ گرهی   
pasraft-e gerehi

Fr.: regression nodale   

For a ring inclined to the planet's equator, the points at which the ring crosses the equator (nodes) slowly move around the planet (regress) in a direction opposite to that of the ring's orbital motion. (Ellis et al., 2007, Planetary Ring Systems, Springer).

nodal; → regression.

gereh (#)

Fr.: nœud   

1) A point of zero → amplitude in a system of → stationary waves. See also → antinode.
2) A → junction point in a network.
3) Same as → orbital node; see also → lunar node.
4) In → graph theory, same as → vertex.

From L. nodus "knot."

Gereh "knot," from Mid.Pers. grih "knot;" Sogdian γr'nš "knot, bond, joining;" Khotanese grantha- "knot;" cf. Skt. granthi- "knot."

nodical month
  ماه ِ گرهی، ~ گوزهری   
mâh-e gerehi (#), ~ gowzahri (#)

Fr.: mois draconitique   

The time interval between two successive passages of the Moon through its ascending node (27.212220 days, i.e., 27 days 5 hours 5 minutes 35.8 seconds). Nodical month is important for predicting eclipses. Also called → draconic month.

Nodical adj. of → node; → month.

Mâh, → month; gerehi, adj. of gereh, → node; gowzahridraconic month.

Noether's theorem
  فربین ِ نوتر   
farbin-e Noether

Fr.: théorème de Noether   

A → symmetry in a physical system leads to a → conserved quantity. For example, symmetry under → translation corresponds to conservation of → momentum, symmetry under → rotation to conservation of → angular momentum, and symmetry in → time to conservation of → energy. The Noether symmetry theorem is a fundamental tool of modern theoretical physics and the calculus of variations, allowing to derive conserved quantities from the existence of variational symmetries.

Named in honor of the German-American woman mathematician Amalie Emmy Noether (1182-1935), who published the theorem in 1918 ("Invariante Variationsprobleme," Nachr. D. König. Gesellsch. D. Wiss. Zu Göttingen, Math-phys. Klasse 1918: 235-257).

nufé (#)

Fr.: bruit   

1) The → random → fluctuations that are always associated with a measurement that is repeated many times over. Any unwanted disturbance, random or → systematic, which contaminates the → signal from an object under study. More specifically:
2) Electronics: An undesired signal within the useful frequency band.
3) Acoustics: Any extraneous sound tending to interfere with the perception of wanted sound.
See also:
atmospheric noise, → background noise, → cosmic radio noise, → dark current noise, → Galactic radio noise, → Johnson-Nyquist noise, → noise source, → noise temperature, → noise voltage, → noise-equivalent power, → photon noise, → quantum noise, → radio noise, → random noise, → readout noise, → receiver noise, → Schottky noise, → shot noise, → signal-to-noise ratio, → speckle noise, → stationary noise, → system noise, → thermal noise, → white noise.

Noise, of obscure origin; it has been related to O.Fr. noise "uproar, brawl," apparently from L. nausea "disgust, annoyance," literally "seasickness." Alternatively the O.Fr. word is traced to L. noxia "hurting, injury, damage."

Nufé "noise," related to Mod.Pers. noyidan "to cry loud, lament," navidan, nâvidan "to lament," noyé, nôyah "plaint, mown," navâ "sound, song," (with prefix *uz-) zenudan, zenav-, zonudan "to wail," Ossetic niwyn/newun "to howl," O.Khotanese nuva- "to make a noise," Yaqnâvi nuyok "crying, howling," novva "sound," Shahmirzâdi nâv- "to cry; cf. Skt. nav- "to sound loudly, roar," náva- "show of joy or triumph;" L. nuntius "messenger," adnuntiare "to annoince;" Tocharian AB nu- "to roar, PIE *neu- "to shout".

noise source
  خن ِ نوفه   
xan-e nufé

Fr.: source de bruit   

An electronic device designed to generate known amounts of radio noise in order to test and calibrate the receivers of radio telescopes.

noise; → source.

noise temperature
  دمای ِ نوفه   
damâ-ye nufé

Fr.: température de bruit   

A means for specifying the noise generated as unwanted → electromagnetic radiation in a receiver system or one of its components. It is usually measured in terms of the equivalent temperature in a → Rayleigh-Jeans spectrum. Noise temperature is used mainly in radio astronomy.

noise; → temperature.

noise voltage
  ولتاژ ِ نوفه   
voltâž-e nufé

Fr.: voltage de bruit   

Fluctuations of electric potential in a physical system due to spontaneous disturbances in the system.

noise; → voltage.

noise-equivalent power
  توان ِ هم‌ارز ِ نوفه   
tavân-e ham-arz-e nufé

Fr.: puissance équivalente de bruit   

A measure of the sensitivity of an electronic detector, defined as the power input to the detector that will create a signal to noise ratio of one for an integration time of half a second.

noise; → equivalent; → power.

nâmgozâri (#)

Fr.: nomenclature   

A set or system of names or terms assigned to objects or items in a particular science or art.

From Fr. nomenclature, from L. nomenclatura "calling of names," from nomenclator, variant of nomenculator "one who announces names, namer," from nomen, → name, + calator "caller," from calare "to call."

Nâmgozâri, from nâm, → name, + gozâri, verbal noun of gozâštan "to place, put; to allow, let," related to gozaštan "to pass, proceed, go over;" Mid.Pers. vitar- "to let pass, lead; to pass;" O.Pers. vitar- "to go across," viytarrayam "I put across;" Av. tar- "to cross over," vī-tərəta- "taken away, isolated;" ultimately Proto-Ir. *ui-tar-.


Fr.: nominal   

1) Of, pertaining to, or constituting a name or names, a noun or nouns.
2) Describing a value quoted for commodity, expectation, or its current estimate, as opposed to the actual value. → nominal value.
3) Within acceptable limits; as expected.
4) a) Grammar: Relating to a noun or to any word or word group that functions as a noun. b) A word which differs from a noun but functions as one.

From L. nominalis "pertaining to a name or names," from nomen "name," cognate with Pers. nâm, as below.

Nâmin, from nâm, → name, + adj. suffix -in.

nominal focal length
  درازای ِ کانونی ِ نامین   
derâzâ-ye kânuni-ye nâmin

Fr.: distance focale nominale   

An approximate value of the → focal length, used for the classification of lenses, mirrors, or cameras, as opposed to the measured one.

nominal; → focal; → length.

nominal value
  ارزش ِ نامین   
arzeš-e nâmin

Fr.: valeur nominale   

The assigned, specified, or intended value of a quantity.

nominal; → value.

nâ- (#)

Fr.: non-   

A prefix meaning "not."

From O.Fr. non-, from L. non "not," from Old L. noenum "not one;" in some cases perhaps from M.E. non "not" (adj.), from O.E. nan.

Nâ- "no, not," variants na, ni, ma- (prohibitive) "not;" from Mid.Pers. nê, ma "no, not;" O.Pers. naiy, nai "not;" Av. nôit, naē "not;" cf. Skt. "not;" cf. L. ne-, in-, un-; Gk. ni; Lith. ; O.C.S. ne "not;" PIE *ne-.

non-algebraic function
  کریای ِ ناجبری   
karyâ-ye nâjabri

Fr.: fonction non algébrique   

A → transcendental function. Examples are: exponential, logarithmic, and trigonometric functions.

non-; → algebraic + → function.

non-baryonic dark matter
  ماده‌ی ِ سیاه ِ ناباریونی   
mâde-ye siyâh-e nâbâriyoni

Fr.: matière noire non-baryonique   

Dark matter composed of → non-baryonic particles.

non-; → baryonic; → dark; → matter.

non-baryonic matter
  مادّه‌ی ِ ناباریونی   
mâdde-ye nâbâriyoni (#)

Fr.: matière non-baryonique   

Matter that, unlike the ordinary matter, is not made of baryons (including the neutrons and protons). It is proposed as a possible constituent of dark matter.

non-; → baryonic matter.

non-coherent radiation
  تابش ِ ناهمدوس   
tâbeš-e nâhamdus (#)

Fr.: rayonnement incohrént   

Radiation having waves that are out of phase in space and/or time; radiation which is not → coherent.

non-; → coherent; → radiation.


Fr.: non contingent   

Describing a → proposition that is either → true in every possible circumstance or → false in every possible circumstance. A proposition that is not → contingent.

non-; → contingent.

non-dispersive medium
  مدیم ِ ناپاشنده   
madim-e nâpâšandé

Fr.: milieu non dispersif   

A medium in which the → phase velocity is independent of frequency.

non-; → dispersive; → medium.

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