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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 699
dewbow
  شبنم‌کمان   
šabnam kamân

Fr.:   

A rainbow formed in the small drops often found on grass in early morning. While the name implies that those drops are dew, that is probably rarely the case. Rather, the drops are usually the result of guttation (the water exuded from leaves as a result of root pressure) rather than dew.

dew; → bow.

dex
  دکس   
deks (#)

Fr.: dex   

A conventional notation for decimal exponent, which converts the number after it into its common antilogarithm; for example, dex (2.35) = 102.35.

From decimal + exponent.

dextro-, dextr-
  راست-   
râst- (#)

Fr.: dextro-, dextr-   

A combining form meaning "right" and "turning clockwise," used in the formation of compound words, e.g. → dextrorotatory, dextrocardia, dextrocular, etc. The variant dextr- occurs before vowels. Compare → levo-.

From L. dextr-, from dexter "right, right-hand;" cf. Gk. dexios "right," dexiteros "located on the right side;" Av. dašina- "right; south" ( Mid.Pers. dašn "right hand; " Ossetic dæsni "skillful, dexterous"); Skt. dáksina- "right; southern;" Goth. taihswo "right hand;" O.Ir. dess "on the right hand, southern;" PIE base *deks- "right;" + epenthetic vowel -o-; see also → south.

Râst- from râst, → right.

dextrorotation
  راست‌چرخش   
râstcarxeš

Fr.: dextrorotation   

The clockwise rotation of the → plane of polarization of light (as viewed by an observer looking straight in the incoming light) by certain substances. See also → levorotation.

dextro-; → rotation.

dextrorotatory
  راست‌چرخ   
râstcarx

Fr.: dextrogyre   

Relating to an → optically active substance that causes → dextrorotation.

Adj. related to → dextrorotation.

di-
  دو-، دی-   
do-, di-

Fr.: di-   

A prefix meaning "two; twice; double." → dimer, → diode, → dipole, → diproton.

L. di, from Gk., → two.

diagonal
  تراکنج   
tarâkonj

Fr.: diagonale   

In a → polygon, a line segment joining any two non-adjacent vertices (→ vertex).

From M.Fr. diagonal, from L. diagonalis, from diagonus "slanting line," from Gk. diagonios "from angle to angle," from dia- "across, dividing two parts" + gonia "angle," related to gony "knee," L. genu "knee," Mod.Pers. zânu "knee," Av. žnav-, žnu- "knee," Skt. janu-; PIE base *g(e)neu-, see below.

Tarâkonj, from tarâ- "across, through," → trans-, + konj "angle, corner, confined place" (variants xong "corner, angle," Tabari kânj, Kurd. kunj, Hamadâni kom), maybe from the PIE base *g(e)neu-, as above, and related to Mod.Pers. zânu "knee" (Av. žnu-), Skt. kona- "angle, corner," Gk. gony, gonia, L. cuneus "a wedge," Albanian (Gheg dialect) kân "angle, corner," Albanian (Toks) kënd "angle, corner."

diagram
  نمودار   
nemudâr (#)

Fr.: diagramme   

A graphic representation of the behavior of one or several variables.

From Fr. diagramme, from L. diagramma, from Gk. diagramma "that which is marked out by lines," from diagraphein "to mark out by lines," from dia- "across, out" + graphein "to write, draw," → -graphy.

Nemudâr agent noun of nemudan "to show," → display, from the past stem nemud + -âr, such as xâstâr, foruxtâr, padidâr, parastâr (contraction of *parastidâr).

diamagnetic
  پادمغناتی   
pâdmeqnâti

Fr.: diamagnétique   

Relative to or characterized by → diamagnetism.

diamagnetism.

diamagnetism
  پادمغنات‌مندی   
pâdmeqnâtmandi

Fr.: diamagnétisme   

The property of a substance, like bismuth, that creates a weak magnetic field in opposition of an externally applied magnetic field, thus causing a repulsive effect. In diamagnetic materials the → magnetic moments of individual atoms are not permanent. Within each atom the electron spins and orbital motions all exactly balance out, so any particular atom has no net magnetic moment. The external magnetic field generates little currents by induction. According to → Lenz's law, the induced magnetic moments of the atoms are directed opposite to the magnetic field.

Diamagnetic, from Gk. dia- a prefix used with several meanings "passing through; thoroughly; completely; going apart," and in the present case "opposed;" → magnetic. magnetic.

Pâdmeqnât, from pâd- "against, contrary," → anti-, + megnâtmagnetism.

diameter
  ترامون   
tarâmun (#)

Fr.: diamètre   

Any chord passing through the center of a figure. The length of this chord.

O.Fr. diamètre, from L. diametrus, from Gk. diametros "diagonal of a circle," from dia- "across, through" + metron "a measure" → meter.

Tarâmun, from tarâ- "across, through," → trans- + mun/mân "measure," as in Pers. terms pirâmun "perimeter," âzmun "test, trial," peymân "measuring, agreement," peymâné "a measure; a cup, bowl," from O.Pers./Av. mā(y)- "to measure," cf. Skt. mati "measures," matra- "measure," Gk. metron "measure," L. metrum; PIE base *me- "to measure."

diamond
  الماس   
almâs (#)

Fr.: diamant   

A crystalline form of → carbon, which is the hardest substance known. Each carbon in a diamond crystal is bonded to four other carbon atoms forming a tetrahedral unit. This tetrahedral bonding of five carbon atoms forms an incredibly strong molecule. Diamond has a very high → refractive index and → dispersive power. It is colorless when pure, and sometimes colored by traces of impurities. Natural diamond was formed billions of years ago within the Earth → mantle at depths greater than 150 km, where pressure is roughly 5 giga→ pascals and the temperature is around 1200 °C. Diamonds reach the surface of the Earth via volcanic eruptions. Similarly very small diamonds (micrometer and nanometer sizes) are usually found in impact sites of → meteorites. Such impact events create shock zones of high pressure and temperature suitable for diamond formation. When diamond is exposed to high temperatures or ion bombardment, it will be transformed into → graphite.

Diamond, from O.Fr. diamant, from M.L. diamant-, diamas-, from L. adamant-, adamas "hardest metal," from Gk. adamas "unbreakable," from → a- "not" + daman "to subdue, to tame;" cognate with Pers. dâm "a tame animal."

Almâs, loanword from Gk., as above.

diamond ring effect
  اسکر ِ انگشتر ِ الماس   
oskar-e angoštar-e almâs

Fr.: effet anneau de diamant   

An intense flash of light that happens a few seconds before and after totality during a solar eclipse. The effect is caused by the last rays of sunlight before totality (or the first rays of sunlight after totality) shining through valleys on the edge of the Moon.

diamond; → ring; → effect.

Oskar, → effect; angoštar "a ring worn on the finger," from angošt "finger," Mid.Pers. angušt "finger, toe," Av. angušta- "toe," from ank- "curved, crooked," cf. Skt. angustha- "thumb," ankah "hook, bent," Gk. angkon "elbow," angkura "anchor," L. angulum "corner" (E. angle), Lith. anka "loop," O.E. ancleo "ankle," O.H.G. ango "hook," PIE base *ang-/*ank- "to bend"; → diamond.

diaphragm
  میان‌بند   
miyânband (#)

Fr.: diaphragme   

A device with a restricted aperture, located in an optical system at any of several points, that cuts off marginal light rays not essential to image formation.

From L.L. diaphragma, from Gk. diaphragma "partition, barrier," from diaphrassein "to barricade," from dia- "across" + phrassein "to fence or hedge in."

Miyânban, from miyân "middle, interior, between" (Mid.Pers. miyân "middle," Av. maiδya-, maiδyāna- "medium, middle," cf. Skt. mádhya- "middle, intemediate," Gk. mesos "middle," L. medius "middle," Goth. midjis, O.E. midd "middle," O.C.S. medzu "between," Arm. mej "middle," PIE *medhyo- "middle," , from base *me- "between") + band "barrier, shutter," from bastan "to bind, shut" (Mid.Pers. bastan/vastan "to bind, shut," Av./O.Pers. band- "to bind, fetter," banda- "band, tie," cf. Skt. bandh- "to bind, tie, fasten," PIE *bhendh- "to bind").

dichotomy
  دوپارگی   
dopâregi

Fr.: dichotomie   

1) General: A division in two parts or kinds that differ widely from or contradict each other.
2) Astro.: The phase of the Moon or a planet when half of its surface appears illuminated by the Sun.

From Gk. dichotomia "cutting in two," from dicho- "apart, in two," combining form of dicha "in two, asunder," akin to → di-, + temnein "to cut."

Dopâregi, from dotwo + pâré "piece, part, portion, fragment" (Mid.Pers. pârag "piece, part, portion; gift, offering, bribe;" Av. pāra- "debt," from par- "to remunerate, equalize; to condemn;" PIE *per- "to sell, hand over, distribute; to assign;" cf. L. pars "part, piece, side, share," portio "share, portion;" Gk. peprotai "it has been granted;" Skt. purti- "reward;" Hitt. pars-, parsiya- "to break, crumble") + -(g)i a noun/state suffix.

dichroic filter
  پالایه‌ی ِ دوفام   
pâlâye-ye dofâm (#)

Fr.: filtre dichroïque   

An → interference filter used to selectively pass light of a small range of colors while reflecting other colors.

dichroism, → filter.

dichroism
  دوفامی   
dofâmi (#)

Fr.: dichroïsme   

Property of some crystals in which radiation polarized in one plane relative to the crystalline axes is freely transmitted, but radiation polarized perpendicular to this is absorbed. Tourmaline is a natural mineral with this property; Polaroid is a synthetic dichroic substance.

From Gk. dichro(os), from di- "two," → di-, + chroma "color" + -ism.

Dofâmi, from do "two," → bi- + fâm "color," + -i noun suffix.

dictionary
  فرهنگ   
farhang (#)

Fr.: dictionnaire   

A reference source in print or electronic form containing words alphabetically arranged along with information about their forms, meanings, pronunciations, etymologies, etc.

M.L. dictionarium "collection of words and phrases," from L. dictionarius "of words," from dictio "word" from dic-, p.p. stem of L. dicere "speak, tell, say," from PIE root *deik- "to point out;" cf. Av. daēs- "to show," daēsa- "sign, omen;" cf. Skt. deś- "to show, point out;" → form.

Farhang, → culture.

dielectric
  نابرق   
nâbarq

Fr.: diélectrique   

A substance in which an electric field gives rise to no net flow of electric charge but to a displacement of charge in opposite directions. The displacement is usually small compared to atomic dimensions. Dielectrics differ from conductors in that they have no free electrons to move through the material under the influence of an electric field. Most insulating materials, e.g. air, porcelain, mica, glass, are dielectrics. A perfect vacuum would constitute a perfect dielectric. → diamagnetic.

Dielectric, from Gk. dia- a prefix used with several meanings "passing through; thoroughly; completely; going apart," and in the present case "not, opposed;" → electric.

Nâbarg, from nâ- "not," → un-, + barqelectricity.

Diesel engine
  موتور ِ دیزل   
motor-e Diesel (#)

Fr.: moteur Diesel   

Any internal combustion → engine in which → adiabatic compression raises the temperature of air high enough so that fuel ignites spontaneously when injected.

After Rudolf Diesel (1858-1913), German engineer; → engine.

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