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ethane etân (#) Fr.: éthane A colorless, odorless → hydrocarbon, C_{2}H_{6}, which occurs with → methane in natural gas. From eth-, from → ethyl, + -ane a suffix used in names of hydrocarbons of the methane or paraffin series. |
ethanol etanol (#) Fr.: éthanol An → alcohol having molecular formula C_{2}H_{5}OH. It is a colorless inflammable liquid with a characteristic odor. Ethanol is produced by fermentation of sugar: C_{6}H_{12}O_{6} → 2 C_{2}H_{5}OH + 2 CO_{2}. It is the active constituent of alcoholic beverages. It is used as a fuel and as a solvent in the extraction of specific substances. It is also known as → ethyl alcohol. Ethanol in the → interstellar medium was first detected toward the → Sagittarius B2 molecular cloud at 82.265, 90.118, and 104.809 GHz (B. Zuckerman et al. 1975, ApJ 196, L99). Short for → ethyl alcohol. |
ether eter (#) Fr.: ether 1) Physics: A hypothetical medium filling all space formerly postulated to
account for the propagation of → electromagnetic radiation
through space. In order to facilitate description and to provide a physical explanation of
various phenomena involving action at a distance and electromagnetism, a medium
had been postulated with mechanical properties adjusted to provide a consistent theory.
In 1887 Michelson and Morley attempted to measure the motion of the Earth
through the ether. No such motion was detected. The
→ Michelson-Morley experiment has been repeated under
different conditions, but the hypothesis of a stationary ether through which the
Earth moves is not verified. From L. æther "the upper air, pure air," from Gk. aither "upper air," from aithein "to burn, shine." |
ether drag kerre-ye eter Fr.: entraînement de l'éther A hypothesis put forward to explain the null measurement of the → ether drift. According to this hypothesis, the Earth somehow drags the ether with it as our planet rotates on its axis and revolves around the Sun. However, the ether drag hypothesis contradicts results from several experiments, including the → aberration of starlight. |
ether drift delek-e eter Fr.: dérive de l'éther 1) The hypothetical motion of the supposed → ether relative to
the Earth. The → Michelson-Morley experiment found no
ether drift. An analogy is given by a boat drifting in a fast-flowing river due
to the river's current. With the same power, the speed would be slower
when sailing across the stream. Moreover, in order to reach
directly opposite the starting point, the boat would have to be headed
somewhat upstream. See also the → ether drag. |
ethno- qowm- (#) Fr.: ethno- A combining form meaning "race, culture, people." From Gk. ethnos "people, nation, class, tribe." Qowm- loan from Ar. qaum "people, tribe, family." |
ethnoastronomy qowm-axtarshenâsi Fr.: ethnologie The study of the beliefs, interpretations, and practices of specific cultures regarding celestial objects or phenomena. Ethnoastronomy uses the tools and methodologies of → ethnology in the study of astronomical conceptions. |
ethnology qowmšenâsi Fr.: ethnologie The study of specific cultures (ethnic groups) in their different aspects (anthropological, social, cultural, etc.) to establish similarities and disparities between them. |
ethyl etil (#) Fr.: éthyl A chemical group, C_{2}H_{5}, produced by removing a hydrogen atom from → ethane. For example, ethyl chloride is C_{2}H_{5}Cl From Ger. Ethyl, from eth-, from → ether, + -yl a suffixed used in the names of radicals. |
ethyl alcohol etil alkol (#) Fr.: éthyl alcool Same as → ethanol. |
etymology riše-šenâsi (#) Fr.: étymologie The study of the origins and history of the form and meaning of → words. M.E., from L. etymologia, from Gk. etymologia, from etymon "true sense" (neuter of etymos) + logos, → -logy. Riše-šenâsi, from rišé "root" (dialectal Tabari rexa; Kurd. regez, riše), from Mid.Pers. rêšak "root," maybe ultimately related to PIE *u(e)rad-, although the Skt. offshoot is absent (Gk. rhiza "root;" L. radix, radius "staff;" O.H.G. wurz "plant, herb;" Ger. Wurz; O.E. rot; E. root) + -šenâsi, → -logy. |
eu- hu- (#) Fr.: eu- A prefix meaning "good, well; true, genuine" (eupepsia; eukaryote); opposed to → dys-. L. from Gk. eu "well," combining form of eus "good" (hu-gies "healthy"); cf. Mid.Pers. hu-; Av. hu- "good;" PIE base *su- "good," see below. Mid.Pers. hu- "good, well" (hu-boy "sweet-smelling," hu-cihr "beautiful," hu-mânih "good-mindedness"); O.Pers. ^{h}u- "good, well" (ukāra- "having good people"); Av. hu-, hū- "well, good, beautiful" (hu-kərp- "well-shapen," hūxta- "well spoken," hu-manah- "good-minded"); Skt. su- "good" (svasti "well-being, good luck," sumánas- "good-minded," sūktá- "well spoken"); Gallic su-; O.S. su-; Welsh hy-; PIE base *su-, as above. |
Euclidean Oqlidosi (#) Fr.: euclidien Of or pertaining to Euclid, or his postulates. → Euclidean division, → Euclidean geometry, → Euclidean space, → non-Euclidean geometry. After the Gk. geometrician and educator at Alexandria, around 300 B.C., who applied the deductive principles of logic to geometry, thereby deriving statements from clearly defined axioms. |
Euclidean division baxš-e Oqlidosi Fr.: division euclidienne In arithmetic, the conventional process of division of two → integers. For a → real number a divided by b > 0, there exists a unique integer q and a real number r, 0 ≤ r <b, such that a = qb + r. |
Euclidean geometry hendese-ye Oqlidosi (#) Fr.: géométrie euclidienne The geometry based on the postulates or descriptions of Euclid. One of the critical assumptions of the Euclidean geometry is given in his fifth postulate: through a point not on a line, one and only one line be drawn parallel to the given line. See also → non-Euclidean geometry. |
Euclidean space fazâ-ye Oqlidosi Fr.: espace euclidean A space in which the → distance between any two points is given by the → Pythagorean theorem: d^{2} = (Δx)^{2} + (Δy)^{2} + (Δz)^{2}, where d is distance and Δx, Δy, and Δz are differential → Cartesian coordinates. Euclidean n-space R^{n} is the set of all column vectors with n real entries. |
Eudoxan spheres sepehrhâ-ye Eudoxus Fr.: sphères d'Eudoxe |
Euler Euler Fr.: Euler Leonhard Euler (1707-1783), the eminent Swiss mathematician, physicist, and astronomer. |
Euler equation hamugeš-e Euler Fr.: équation d'Euler In → fluid mechanics, one of a set of → differential equations that govern the motion of a → compressible, → inviscid fluid. Euler equations correspond to the → Navier-Stokes equations with zero → viscosity. |
Euler line xatt-e Euler Fr.: droite d'Euler In any → triangle, the straight line on which always lie the → centroid, → circumcenter, and → orthocenter. |
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