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Aristarchus' inequality nâhamugi-ye Aristarchus Fr.: inégalité d'Aristarque Put in modern notation, if α and β are acute angles and if β <α, then sin α / sin β <α / β < tan α / tan β. Aristarchus probably used this inequality to show that the Sun is between 18 and 20 times as far from the Earth as the Moon is. Aristarchus of Samos (c.310-c.230 BC); → inequality. |
Aristotelian form dise-ye Arastuyi Fr.: forme aristotelienne Any of the four main → proposition
forms treated in Aristotle's → syllogism: Greek philosopher Aristotle (384-322 BC); → form. |
arithmetic hesâb (#) Fr.: arithmétique A branch of mathematics that deals usually with integers, rational numbers, real numbers, or complex numbers under addition, subtraction, multiplication, and division. See also → compute, → computation, → count, → calculate, → calculus, → mathematics, → statistics. O.Fr. arsmetique, from M.L. arithmetica, from Gk. arithmetike (tekhne) "(art, skill) of numbers," from arithmos "number." Hesâb, from Ar. hisab. |
arithmetic mean miyângin hesâbi (#) Fr.: moyenne arithmétique Of n numbers a_{1}, a_{2}, ..., a_{n}, the quantity defined as: (a_{1} + a_{2} + ... + a_{n})/n. → arithmetic; → mean. |
arithmetic progression farâyâzi-yz hesâbi (#) Fr.: progression arithmétique A → sequence of n numbers or quantities such that the difference between any two successive terms is a constant. In particular, if a is the first term, the nth term is a + (n - 1)d, where d is the constant. Also called → arithmetic sequence. → arithmetic; → progression. |
arithmetic sequence peyâye-ye hesâbi Fr.: suite arithmétique → arithmetic; → sequence. |
arm 1) ârm; 2, 3) bâzu (#) Fr.: bras 1) Each of the upper limbs of the human body, especially the part between
the → shoulder and the
→ wrist. M.E. arm, from O.E. earm "arm," from P.Gmc. *armaz (cf. M.Du., Ger. Arm, O.N. armr, O.Fris. erm), from PIE base *ar- "to fit, join;" cf. Mod.Pers. arm, as below. 1) Ârm (Dehxodâ, Steingass) "arm, from the elbow to the shoulder;"
Av. arma-, arəmo- "arm;" cf. Ossetic ärm "hand;"
Armenian armuku "elbow;" Skt. irma- "arm;"
Gk. arthron "a joint;" L. armus "shoulder;" cognate with E.
arm, as above. |
armillary sphere zâtolhelaq (#) Fr.: sphère armillaire An ancient instrument, used since ancient times until the Middle ages and later, to determine positions of celestial bodies. It consisted of an assemblage of rings, all circles of the same sphere, designed to represent the positions of the important circles of the celestial sphere. L. armillarius, from armilla "arm ring, bracelet," from armus "arm" + → sphere. Zâtolhelaq from Ar. "multi-ringed," from zât "holder, keeper" + helaq "rings," from halqah "ring." |
Arnett's rule razan-e Arnett Fr.: règle d'Arnett The → peak luminosity of a → Type Ia supernova is proportional to the rate of → radioactive decay and hence directly proportional to the mass of ^{56}Ni. Arnett, W. D. 1982, ApJ, 253, 785; → rule. |
aromatic aromatik Fr.: aromatique Chemistry: Of, relating to, or containing the six-carbon ring typical of the benzene (C_{6}H_{6}) series and related organic groups. M.E. aromatyk, from M.Fr. aromatique, from L. aromaticus, from Gk. aromatikos, from aroma "seasoning, sweet spice," of unknown origin. |
aromatic compound candsâxt-e aromâtik Fr.: composé aromatique An organic compound which contains benzene rings in its structure. The simplest is therefore benzene (C_{6}H_{6}). Aromatic compounds have a planar ring of atoms linked by alternate single and double bounds. |
Aromatic Infrared Band (AIB) bând-e forusorx-e aromâtik Fr.: bande infrarouge aromatique A family of strong infrared emission bands at 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 μm which are widely observed in a large variety of objects, such as → H II regions, → reflection nebulae, → planetary nebulae, and the → diffuse interstellar medium of our galaxy and other galaxies. Solar system objects, such as carbonaceous → meteorites and → interplanetary dust particles are also known to display these features. They are suggested to be due to → polycyclic aromatic hydrocarbons. |
arrange rezgidan Fr.: arranger, ranger 1) To set in a rank or row. To put in order. From M.E. arayngen, from M.Fr. arangier, from O.Fr. arengier, from a- "to," → ad-, + rangier "set in a row," from rang, → rank. Rezgidan "to set in a row," from Lori rezg "row," related to râst, → right, Av. rāz- "to direct, draw a line;" probably ultimately from Proto-Ir. *Hrazaka- "row." |
arrangement rezgmân Fr.: arrangement The act of arranging or being arranged. Result or manner of arranging. Verbal noun of → arrange. |
array ârast Fr.: réseau; tableau 1) A system of telescopes coupled together, using → interferometric
techniques, to increase the angular resolution or the sensitivity. Array, from M.E. arraien, from Anglo-Norman arraier, from V.L. *arredare. Ârast "set in order," from ârastan, ârâstan "to set in order," Mid.Pers. ârây-, ârâstan, from â- + Av. râd- "to make ready, prepare;" PIE *ar- "to fit together." |
Arrhenius equation hamugeš-e Arrhenius Fr.: équation d'Arrhenius An important relationship in physical chemistry that combines the concepts of → activation energy and the → Maxwell-Boltzmann distribution law. It is expressed by: k = Ae^{-Ea/(RT)}, where k is the chemical → reaction rate, E_{a} is the activation energy, R is the → gas constant, and T is → temperature. Named for Svante Arrhenius (1859-1927), Swedish chemist and physicist who suggested the relationship in 1889. |
arrival time zamân-e raseš Fr.: temps d'arrivée The precise time at which the gamma burst photons hit a detector. Measuring the time difference between the arrival time of the photons at different telescopes separated by known distances permits to determine the burst direction. Arrival, n. from arrive + → -al. Arrive, from O.Fr. ariver "to come to land," from V.L. *arripare "to touch the shore," from L. ad ripam "to the shore," from → ad "to" + ripa "shore;" → time. Zamân, → time; raseš n. from rasidan "to arrive," Mid.Pers. rasitan, O.Pers./Av. rasa- present stem of ar- "to move, go or come toward," cf. Skt. ar-, rcchati. |
arrow peykân (#) Fr.: flèche A slender, straight, generally pointed missile or weapon made to be shot from a bow and equipped with feathers at the end of the shaft near the → nock, for controlling flight (Dictionary.com). → Sagitta. M.E. arewe, arwe, O.E. earh, possibly borrowed from O.N. ör; ultimately from PIE *arku- "bow and/or arrow," → arc. Peykân "arrow, javelin" (cognate with afkan-, afkandan "to throw, cast away," parâkan-, parâkandan "to scatter, to disperse"), ultimately from Proto-Iranian *paiti-kan- "to throw against," from *paiti- "against, opposite, back" (cf. Mod.Pers. pâd- "against, contrary to;" Mid.Pers. pât-; O.Pers. paity "against, back, opposite to, toward, face to face, in front of;" Av. paiti; Skt. práti "toward, against, again, back, in return, opposite;" Pali pati-; Gk. proti, pros "face to face with, toward, in addition to, near;" PIE *proti) + *kan- "to throw." |
arsenic ârsenik (#) Fr.: arsenic A silver-gray black metallic → chemical element which is very brittle; symbol As. → Atomic number 33; → atomic weight 74.9216; → boiling point 613.0 °C (sublimation); → valence -3, 0, +3, or +5. The uncombined element is not considered poisonous, but many of its compounds are extremely so, and are used in medicine and for destroying pests. Its longest-lived radioactive → isotope, ^{73}As, has a → half-life of 80.3 days. M.E. arsenik, from O.Fr. arsenic, from L. arsenicum, from Gk. arsenikon "arsenic," adapted from Syriac (al) zarniqa "arsenic," from Mid.Pers. zarnik "arsenic," literally "gold-colored," probably because of the lemon-yellow color of arsenic trisulphide (Mod.Pers. zarnix, zarni "arsenic"), from zarr, zar "gold" (+ -ik→ -ic); Av. zaranya-, zarənu- "gold;" O.Pers. daraniya- "gold;" cf. Skt. hiranya- "gold;" also Av. zaray-, zairi- "yellow, green;" Mod.Pers. zard "yellow;" Skt. hari- "yellow, green;" Gk. khloe literally "young green shoot;" L. helvus "yellowish, bay;" Rus. zeltyj "yellow;" P.Gmc. *gelwaz; Du. geel; Ger. gelb; E. yellow. Ârsenik, loan from Fr., as above. |
art honar (#) Fr.: art The process or product of human activity which is the expression of creativity and/or imagination that appeals to the senses or emotions. From O.Fr. art, from L. artem, (nominative ars) "art, skill, craft;" from PIE base *ar- "to fit, join;" cf. Mod.Pers. arm "arm, from the elbow to the shoulder;" Av. arma-, arəmo- "arm;" Skt. irma- "arm;" Gk. arthron "a joint;" L. armus "shoulder." Honar, from Mid.Pers. hunar "skill, ability, virtue, manliness;" O.Pers. hūnarā- "abilities, skills;" Av. hunara- "ability, skill"; cf. Skt. sūnára- "powerful, joyous, beautiful;" Proto-Iranian *Hnar- "to be able, strong." |
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