An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 685

Fr.: dihédral   

1) Having formed by two half-planes which intersect.
2) Of or relating to a → dihedron.

dihedron; → -al.

dihedral angle
  زاویه‌ی ِ دودیمی   
zâviye-ye dodimi

Fr.: angle dièdre   

An angle formed by two planes meeting along a common line. Compare with → face angle.

angle; → dihedral.


Fr.: dièdre   

A figure formed by two intersecting planes.

di-; → -hedron.

  ۱) فراخاندن؛ ۲) فراخیدن   
1) farâxândan; 2) farâxidan (#)

Fr.: 1) dilater; 2) se dilater   

1) ( To make wider or larger; cause to expand.
2) (v.intr.) To spread out; expand.

M.E. dilaten, from O.Fr. dilater, from L. dilatare "make wider, enlarge," from → dis- "apart" + latus "wide," → latitude.

Farâxândan, farâxidan, infinitive from farâx "broad, wide, spacious;" Mid.Pers. frâxv, fraxv "broad, wide," frâxvitan, frâxvênitan "to spread."

farâxeš (#)

Fr.: dilatation   

The act of dilating; state of being dilated. Also dilatation.
Physics: The increase in volume per unit volume of a homogeneous substance. → time dilation.

Verbal noun of → dilate.

  ۱) اوتال؛ ۲) اوتالیدن   
1) owtâl; 2) owtâlidan

Fr.: 1) dilué; 2) diluer   

1) (adj.) Describing a solution that is reduced in concentration.
2) ( To make a solution thinner by the addition of water or the like.

From L. dilutus, p.p. of diluere "dissolve, wash away," from → dis- "apart" + -luere, combining form of lavere "to wash;" cf. Pers. lur "flood" [Mo'in, Dehxodâ] (variants Lori, Kordi: laf, lafow, lafaw, Tabari: ); Gk. louein "to wash;" Bret. laouer "trough;" PIE base *lou- "to wash."

Owtâl, from Tabari utâl, "having water, impregnated with water, waterlogged," from ow "water," → water + tâl variant of dâr "having, possessor," from dâštan "to have, to possess" (Mid.Pers. dâštan; O.Pers./Av. root dar- "to hold, keep back, maitain, keep in mind;" Skt. dhr-, dharma- "law;" Gk. thronos "elevated seat, throne;" L. firmus "firm, stable;" Lith. daryti "to make;" PIE base *dher- "to hold, support").


Fr.: dilution   

The process of reducing the concentration of solute in a solution by increasing the proportion of solvent.

Verbal noun of → dilute.

dilution factor
  کروند ِ اوتالش   
karvand-e owtâleš

Fr.: facteur de dilution   

The energy density of a radiation field divided by the equilibrium value for the same color temperature.

dilution; → factor.

tiré (#)

Fr.: faible, pâle, mat(e)   

Not bright; obscure from lack of light.

O.E. dimm "dark, gloomy, obscure," from P.Gmc. *dimbaz.

Tiré, from Mid.Pers. têrag, variant of târig "dark," Av. taθra- "darkness," taθrya- "dark," cf. Skt. támisrâ- "darkness, dark night," L. tenebrae "darkness," Hittite taš(u)uant- "blind," O.H.G. demar "twilight."


Fr.: dimension   

1) Math.: Independent extension in a given direction; a property of space.
2) Physics: → physical dimension.

From L. dimensionem (nom. dimensio), from stem of dimetri "to measure out," from → dis- + metri "to measure."

Vâmun, from vâ-, → dis-, + mun, variant 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;" PIE base *me- "to measure;" cf. Skt. mati "measures," matra- "measure;" Gk. metron "measure;" L. metrum.


Fr.: dimensionnel   

Of or pertaining to → dimension.

dimension; → -al.

dimensional analysis
  آنالس ِ وامونی، آناکاوی ِ ~   
ânâlas-e vâmuni, ânâkâvi-ye ~

Fr.: analyse dimensionnelle   

A technique used in physics based on the fact that the various terms in a physical equation must have identical → dimensional formulae if the equation is to be true for all consistent systems of unit. Its main uses are:
a) To test the probable correctness of an equation between physical quantities.
b) To provide a safe method of changing the units in a physical quantity.
c) To solve partially a physical probable whose direct solution cannot be achieved by normal methods.

dimensional; → analysis.

dimensional formula
  دیسول ِ وامونی   
disul-e vâmuni

Fr.: formule dimensionnelle   

Symbolic representation of the definition of a physical quantity obtained from its units of measurement. For example, with M = mass, L = length, T = time, area = L2, velocity = LT-1, energy = ML2T-2. → dimensional analysis.

dimensional; → formula.

dimensionless quantity
  چندی ِ بی‌وامون   
candi-ye bivâmun

Fr.: quantité sans dimension   

A quantity without an associated → physical dimension. Dimensionless quantities are defined as the ratio of two quantities with the same dimension. The magnitude of such quantities is independent of the system of units used. A dimensionless quantity is not always a ratio; for instance, the number of people in a room is a dimensionless quantity. Examples include the → Alfven Mach number, → Ekman number, → Froude number, → Mach number, → Prandtl number, → Rayleigh number, → Reynolds number, → Richardson number, → Rossby number, → Toomre parameter. See also → large number.

dimension + -less M.E. from O.E. læs (adv.), læssa (adj.), akin to O.Fr. les "less."

Bi- "without," → a-, + vâmun, → dimension.


Fr.: dimère   

A molecule resulting from combination of two identical molecules.

From → di- "two, twice, double," + -mer a combining form denoting member of a particular group, → isomer.

diod (#)

Fr.: diode   

An electronic component with two active terminals, an → anode and a → cathode, through which current passes in one direction (from anode to cathode) and is blocked in the opposite direction. Diodes have many uses, including conversion of → alternating current to → direct current, regulation of votage, and the decoding of audio-frequency signals from radio signals.

di- "two, twice, double," + hodos "way."

Dione (Saturn IV)

Fr.: Dioné   

The fourth largest moon of Saturn and the second densest after Titan. Its diameter is 1,120 km and its orbit 377,400 km from Saturn. It is composed primarily of water ice but must have a considerable fraction of denser material like silicate rock.

Discovered in 1684 by Jean-Dominique Cassini, Italian born French astronomer (1625-1712). In Gk. mythology Dione was the mother of Aphrodite (Venus) by Zeus (Jupiter).

dioptr (#)

Fr.: dioptre   

A unit of optical measurement that expresses the refractive power of a lens or prism. In a lens or lens system, it is the reciprocal of the focal length in meters.

L. dioptra, from Gk. di-, variant of dia- "passing through, thoroughly, completely" + op- (for opsesthai "to see") + -tra noun suffix of means.

Dioptr loanword from Fr.


Fr.: dioptra   

An instrument used in antiquity to measure the apparent diameter of the Sun and the Moon. It was a rod with a scale, a sighting hole at one end, and a disk that could be moved along the rod to exactly obscure the Sun or Moon. The Sun was observed directly with the naked eye at sunrise or sunset in order to prevent eye damage. Aristarchus (c.310-230 B.C.), Archimedes (c. 290-212 B.C.), Hipparchus (died after 127 B.C.), and Ptolemy (c.100-170 A.D.) used the dioptra. The instrument could also serve for measurement of angles, land levelling, surveying, and construction of aqueducts and tunnels.


našib (#)

Fr.: inclinaison   

1) Navigation: The angular difference between the visible horizon and the true horizon. Same as → dip of the horizon.
2) Geodesy: The angle between the horizontal and the lines of force of the Earth's magnetic field at any point. → magnetic dip.
3) Aviation: The angle between the true and apparent horizon, which depends on flight height, the Earth's curvature, and refraction.

O.E. dyppan "to immerse," cognate with Ger. taufen "to baptize," and with → deep.

Našib, → depression.

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