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dihedral dodime-yi Fr.: dihédral 1) Having formed by two half-planes which intersect. |
dihedral angle zâviye-ye dodimi Fr.: angle dièdre An angle formed by two planes meeting along a common line. Compare with → face angle. |
dihedron dodimé Fr.: dièdre A figure formed by two intersecting planes. |
dilate 1) farâxândan; 2) farâxidan (#) Fr.: 1) dilater; 2) se dilater 1) (v.tr.) To make wider or larger; cause to 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." |
dilation farâxeš (#) Fr.: dilatation The act of dilating; state of being dilated. Also dilatation. Verbal noun of → dilate. |
dilute 1) owtâl; 2) owtâlidan Fr.: 1) dilué; 2) diluer 1) (adj.) Describing a solution that is reduced in concentration. 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: lé); 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"). |
dilution owtâleš 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 karvand-e owtâleš Fr.: facteur de dilution The energy density of a radiation field divided by the equilibrium value for the same color temperature. |
dim 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." |
dimension vâmun Fr.: dimension 1) Math.: Independent extension in a given direction; a property of space. 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. |
dimensional vâmuni Fr.: dimensionnel Of or pertaining to → dimension. |
dimensional analysis 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: → dimensional; → analysis. |
dimensional formula 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 = L^{2}, velocity = LT^{-1}, energy = ML^{2}T^{-2}. → dimensional analysis. → dimensional; → formula. |
dimensionless quantity 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." |
dimer dimer 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. |
diode 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) Dioné 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). |
diopter 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. |
dioptra dioptrâ 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. → diopter. |
dip našib (#) Fr.: inclinaison 1) Navigation: The angular difference between the visible horizon and
the true horizon. Same as → dip of the horizon. O.E. dyppan "to immerse," cognate with Ger. taufen "to baptize," and with → deep. Našib, → depression. |
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