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natural line broadening pahneš-e zâstâri-ye xatt Fr.: élargissement naturel de raie The broadening of any spectral line due to the fact that excited levels have mean lives, which, by virtue of the uncertainty principle, implies a spread in the energy values. → natural; → line; → broadening. |
natural logarithm logâritm-e zâstâri Fr.: logarithme naturel The logarithm in which the → base is the → irrational number e = 2.718281828.... Also called → Napierian logarithm. The natural logarithm is denoted ln, an abbreviation of logarithmus naturalis. Natural logarithms are related to → common logarithms through: ln x = (1/M) log x, with M = (1/ln 10) ≅ 0.434294. |
natural number adad-e zâstâri Fr.: nombre naturel Either a member of the set of positive integers 1, 2, 3, ..., or the set of non-negative integers 0, 1, 2, 3, ... There seems to be no general agreement about whether to include 0 in the set of natural numbers. |
natural period dowre-ye zâstâri Fr.: période naturelle Of a body or system, the period of → free oscillation. |
natural resonance bâzâvâyi-ye zâstâri Fr.: résonance naturelle A resonance such that the period of the driving force is the same as the natural period of the system. |
natural satellite mâhvâre-ye zâstâri Fr.: satellite naturel A solar system → object that → revolves around a → primary body and is not man made. |
natural science dâneš-e zâstâri Fr.: science naturelle A science that deals with matter, energy, their interrelations and transformations, In other words, natural sciences are concerned with physical processes observable in nature. They can be divided into physical and biological sciences. |
natural units yekâhâ-ye zâstâri Fr.: unités naturelles Physical units of measurement defined in terms of universal physical constants in such a manner that some chosen physical constants (e.g. the speed of light, Planck's constant, Boltzmann's constant, etc.) are equal to unity. The use of natural units allows these constants to be omitted from mathematical equations, leading to simpler calculations. |
natural uranium urâniom-e zâstâri Fr.: uranium naturel Uranium as found in nature. It contains 0.7% uranium-235, 99.3% uranium-238, and a trace of uranium-234 by weight. |
naturalism zâstâr-gerâyi, zâstâr-bâvari Fr.: naturalisme Philosophy: 1) The view of the world that takes account only of natural elements
and forces, excluding the supernatural or spiritual. |
nature zâstâr Fr.: nature The natural world as it exists without human beings or civilization. M.E. natur(e), from O.Fr. nature from L. natura "the things at the outset, as it was when brought into existence; conditions of birth; essence, natural qualities," from natus "born," p.p. of nasci "to be born," from PIE *gen- "to give birth, beget," cognate with Pers. zâdan "to give birth," as below. Zâstâr, literally "birth," from zâst past stem of [Dehxodâ] zâstan, variant of zâdan "to bring forth, give birth;" (Lâsgardi, Sorxeyi, Aftari) nestor "barren, sterile" (Mid.Pers. zâtan; Av. zan- "to bear, give birth to a child, be born," infinitive zazāite, zāta- "born;" cf. Skt. janati "begets, bears;" L. gignere "to beget," nasci "to be born," as above, PIE base *gen- "to give birth, beget") + suffix -âr (forming verbal nouns as in raftâr, kerdâr, goftâr, didâr, jostâr, and so on; or forming accusative nouns, as in gereftâr, koštâr, etc.). |
nautical astronomy axtaršenâsi-ye daryâ-navardik Fr.: astronomie nautique The branch of practical astronomy concerned with the determination of position and direction on sea by observation of celestial objects. Nautical, from M.Fr. nautique, from L. nauticus "pertaining to ships or sailors," from Gk. nautikos, from nautes "sailor," from naus "ship," from PIE *nau- "boat;" cf. Pers. nâv "ship;" O.Pers./Av. *nāv-, O.Pers. nāviyā- "fleet;" Skt. nau-, nava- "ship, boat;" → astronomy. Axtaršenâsi→ astronomy; daryâ-navardik, relating to daryâ-navardi "sea navigation," from daryâ "sea" (Mid.Pers. daryâp variant zrah; O.Pers. drayah-; Av. zrayah- "sea;" cf. Skt. jráyas- "expanse, space, flat surface") + navardi, noun of navardidan, navardan "to travel, walk, pass by and over" + -ik, → -ic. |
nautical twilight nimtâb-e daryâ-navardik Fr.: crépuscule nautique The period before sunrise and after sunset when the center of the Sun's disk is between 6° and 12° below the horizon. → nautical astronomy; → twilight. |
Navier-Stokes equation hamugeš-e Navier-Stokes Fr.: équation de Navier-Stokes One of a set of differential equations that describes the motion of a fluid as a function of pressure, density, total external force, and viscosity. → Euler equation. Named after Claude-Louis Navier (1785-1836), a French engineer and physicist, and George Gabriel Stokes (1819-1903), an English mathematician and physicist; → equation. |
navigational astronomy axtaršenâsi-ye nâvrâni Fr.: astronomie nautique Same as → nautical astronomy. Navigational, adj. of navigation, from L. navigationem (nom. navigatio), from navigatus, p.p. of navigare "to sail, steer a ship," from navis "ship," cognate with Pers. nâv "ship," as below, + root of agere "to drive," → act; → astronomy. Axtaršenâsi→ astronomy; nâvrâni "navigation," from nâv "ship;" O.Pers./Av. *nāv-, O.Pers. nāviyā- "fleet;" cf. Skt. nau-, nava- "ship, boat" + râni verbal noun of rândan "to drive, to cause to go," causative of raftan "to go, walk, proceed" (present tense stem row-, Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack"). |
neap tide kehkešand (#) Fr.: marée de morte-eau Tide which occurs during the → first quarter and → third quarter of the → Moon when the pull of the Sun is at → right angles to that of the Moon. Neap, from M.E. neep, from O.E. nepflod "neap tide" + → tide. Kehkešan "small tide," from keh- "small, little," → low, + kešand, → tide. |
near nazdik (#) Fr.: proche Close; to a point or place not far away. O.E. near "closer, nearer," comparative of neah, neh "nigh." Nazdik, from Mid.Pers. nazdik "near," from nazd "close" (Mid.Pers. nazd, nazdik "near," nazdist "first;" O.Pers. ašna- "close;" Av. nazdišta- "nearest, next," nazdyo "nearer to," nas- "to come near, approach, reach;" cf. Skt. nédīyas- "closer, very close," nas- "to approach, to reach") + -ik, → -ic. |
near ultraviolet farâbanafš-e nazdik (#) Fr.: proche ultraviolet The longest wavelengths of the ultraviolet region, which are adjacent to the visible, from 200 to 350 nm. → near; → ultraviolet. |
near-Earth asteroid (NEA) sayyârak-e zamin-nazdik Fr.: astéroïde géocroiseur An → asteroid whose orbit lies partly between 0.983 and 1.3 → astronomical units from the Sun, so that it passes close to the Earth. Currently thousands of near-Earth asteroids are known, ranging in size up to about 30 km. Among them, there are between 500 and 1,000 such asteroids larger than one km in diameter. They are divided into three subclasses: → Amor asteroids, → Apollo asteroids, and → Aten asteroids. See also → near-Earth object. |
near-Earth object (NEO) barâxt-e zamin-nazdik Fr.: géocroiseur An → asteroid, → comet, or large → meteoroid whose orbit brings it exceptionally close to the Earth, and which may therefore pose a collision danger. Most such objects are in orbits around the Sun with → perihelion distance less than 1.3 → astronomical units. See also → near-Earth asteroid. |
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