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."
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
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.
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.
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").
1) General: A division in two parts or kinds that differ widely from or contradict
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 do→ two + 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.
pâlâye-ye dofâm (#)
Fr.: filtre dichroïque
An → interference filter used to selectively pass light of a small range of colors while reflecting other colors.
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.
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.
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.
motor-e Diesel (#)
Fr.: moteur Diesel
After Rudolf Diesel (1858-1913), German engineer; → engine.
Fr.: équation de Dieterici
An → equation of state for → real gases which leads to the → van der Waals equation as a → first approximation. It is of the form P(V - b) [exp (a/VRT)] = RT, where P is the pressure, V is the volume, T is the thermodynamic temperature, R is the → gas constant, and a and b are the constants characteristic of the gas.
Named after Conrad Dieterici (1858-1929), a German physicist; → equation.
degarsân budan (#)
Fr.: différer, être différent
To be unlike, dissimilar, or distinct in nature or qualities.
From O.Fr. différer, from L. differre "to set apart, differ," from → dis- "away from" + ferre "to carry, bear" (cf. Av. baraiti "carries," O.Pers. barantiy "they carry," Mod.Pers. barad "carries," Skt. bharati "carries," Arm. berem "I carry," Gk. pherein "to carry," O.E., O.H.G. beran, Rus. brat' "to take," bremya "a burden").
Degarsân "different," from degar "another, other" (Mid.Pers. dit, ditikar "the other, the second," O.Pers. duvitiya- "second," Av. daibitya-, bitya- "second," Skt. dvitiya- "second," PIE *duitiio- "second") + sân "manner, semblance" (variant sun, Mid.Pers. sân "manner, kind," Sogdian šôné "career") + budan "to be" (Mid.Pers. budan, from O.Pers./Av. bav- "to be; become, take place," Av. buta- perf. ptcpl. pass., bavaiti "becomes," Skt. bhavati "becomes, happens," bhavah "becoming; condition, state," PIE *bheu- "to be, come into being, become;" cf. Gk. phu- "become," phuein "to bring forth, make grow," L. fui "I was" (perf. tense of esse), futurus "that is to be, future," Ger. present first and second person sing. bin, bist, E. to be, O.Ir. bi'u "I am," Lith. bu'ti "to be," Rus. byt' "to be").
The quality or condition of being different.
Noun form of → differ.
Not alike in character or quality; differing; dissimilar.
Adj. of → difference.
Of a mathematical function, the quality of being → differentiable.
Noun from → differentiable.
karyâ-ye degarsânipazir, ~ degarsânidani
Property of a mathematical function if it has a → derivative at a given point.
1) degarsâné; 2) degarsâneyi
Degarsâné, from degarsân, → different + noun suffix -é.
differential and integral calculus
afmârik-e degarsâne-yi va dorostâli
Fr.: calcul différentiel et intégral
afmârik-e degarsâneyi, ~ degarsânehâ
Fr.: calcul différentiel
A branch of calculus which is concerned with the instantaneous rate of change of quantities with respect to other quantities, or more precisely, the local behavior of functions. → integral calculus.