# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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 potential energy   کاروژ ِ توند   kâruž-e tavandFr.: énergie potentielle   Of a system, the work done in changing the system from some standard configuration to its present state. Thus, if a body of mass m is raised vertically through a height h, the work done, mgh, is the increase in potential energy.→ potential; → energy. potential energy curve   خم ِ کاروژ ِ توند   xam-e kâruž-e tavandFr.: courbe de l'energie potentielle   A plot that displays the → potential energy of a moving body as a function of its position. It is explained by the → conservation of energy and the conversion of potential energy into → kinetic energy and vice versa.→ potential; → energy; → curve. potential field   میدان ِ توند   meydân-e tavandFr.: champ de potentiel   A field that has a → potential. A continuous → vector fieldA in a domain D is a potential field in D if and only if its → work around every closed curve C contained in D is zero: ∫A.ds = 0. Examples include the → gravitational field and the → electrostatic field.→ potential; → field. potential gradient   زینه‌ی ِ توند   zine-ye tavandFr.: gradient de potentiel   At a point, the rate of change of potential V, with distance x, measured in the direction in which the variation is a maximum. The intensity F of the field is proportional to the potential gradient, but is oppositely directed: F = -dV/dx.→ potential; → gradient. potential well   چاه ِ توند   câh-e tavandFr.: puit de potentiel   Region in a → field of force in which the potential decreases abruptly, and in the surrounding region of which the potential is larger.→ potential; → well. potentiality   توندی   tavandiFr.: potentialité   1) The state or quality of being potential. Something potential. 2) According to Aristotle, what has the possibility of having → form, in contrast to → actuality; the power to effect change.→ potential + → -ity. potentially   توندانه   tavandânéFr.: potentiellement   With a possibility of becoming actual; possibly.→ potential; → -ly. potentially hazardous asteroid (PHA)   سیارک ِ توندانه آپه‌ناک   seyyârak-e tavandâné âpenâkFr.: astéroïde potentiellement dangereux   An asteroid that could make a threatening close approach to the Earth. In technical terms a PHA is defined as having an → absolute magnitude of 22 or brighter and an → Earth Minimum Orbit Intersection Distance (MOID) of less than 0.05 → astronomical unit or 7.5 million km.→ potentially; → hazardous; → asteroid. potentiometer   توندسنج   tavandsanjFr.: potentiomètre   An instrument for measuring electrical quantities by balancing an unknown potential difference against a known potential difference.From potenti(al), → potential + -o + → -meter. power   توان   tavân (#)Fr.: puissance, pouvoir   1) Physics: The → rate of doing → work on transferring → energy, as expressed in ergs/sec, watts, etc. Same as → mechanical power. 2) Math.: An → exponent to which a given quantity is raised. The expression xn is therefore known as "x to the n-th power."M.E. pouer(e), poer(e), from O.Fr. povoir, noun use of the infinitive in O.Fr., "to be able," from V.L. *potere, from L. potis "powerful, able, capable;" cognate with Av. paiti- "lord, husband;" Mod.Pers. -bad (sepah-bad "general, commander of an army"); Skt. pái- "master, husband;" Gk. posis "husband;" Lith. patis "husband."Tavân "power, strength," tavânestan "to be powerful, able;" Mid.Pers. tuwan "power, might," from O.Pers./Av. base tav- "to have power, to be strong, to be able," Av. tavah- "power," təviši- "strength," Mod.Pers. tuš, tâb "power, ability," O.Pers. tauman- "power, strength," tunuvant- "powerful," Skt. tu- "to be strong, to have authority," tavas-, tavisa- "strong, energetic," tavisi- "power, strength." power function   کریای ِ توانی   karyâ-ye tavâniFr.: fonction de puissance   A function of the form f(x) = xn, where n is a → real number.→ power; → function. power law   قانون ِ توانی   qânun-e tavâni (#)Fr.: loi de puissance   A mathematical relationship between two quantities expressed by a → power function.→ power; → law. power series   سری ِ توانی   seri-ye tavâni (#)Fr.: série de puissance   A series in which the terms contain regularly increasing powers of a variable. In general, a0 + a1x + a2x2 + ... + anxn, where a0, a1, etc. are constants.→ power; → series. power spectral density   چگالی ِ بینابی ِ توان   cagâli-ye binâbi-ye tavânFr.: densité spectrale de puissance   Same as → spectral density.→ power; → spectral; → density. power spectrum   بیناب ِ توانی   binâb-e tavâni (#)Fr.: spectre de puissance   The plot that gives the portion of a signal's power falling within given frequency bins. The most common way of generating a power spectrum is by using a discrete Fourier transform.→ power; → spectrum. power-law distribution   واباژش با قانون ِ توانی   vâbâžeš bâ qânun-e tavâniFr.: distribution en loi de puissance   For a → random variable X, any → distribution which has the form: P(X ≥ x) = (k/x)α, where x is a value in the range defined for X, k > 0 is a parameter termed location parameter, and α > 0 is the → slope parameter.→ power; → law; → distribution. power-law elliptical galaxy   کهکشان ِ بیضی‌گون با قانون ِ توانی   kahkešân-e beyzigun bâ qânun-e tavâniFr.: galaxie elliptique en loi de puissance   An → elliptical galaxy whose → surface brightness can be approximated by a single → power law at small radii (r ≤ 10-20''). More modern interpretations have emphasized that these profiles can be better understood as the inward continuation of the galaxy's overall → Sersic profile, usually modified by an additional, nuclear-scale stellar component (S. P. Rusli et al., 2013, AJ 146, 160).→ power; → law; → galaxy. Poynting vector   بردار ِ پوینتینگ   bordâr-e PoyntingFr.: vecteur de Poynting   The amount of electromagnetic energy flowing through unit area, perpendicular to the direction of energy propagation, per unit time, given by (c/2 π)[E x H]. → Poynting's theorem. Poynting's theorem   فربین ِ پوینتینگ   farbin-e PoyntingFr.: théorème de Poynting   The space through which electromagnetic radiation passes is filled with electric and magnetic fields at right angles to each other and to the direction of propagation of the radiation. The rate of energy transfer is given by the Poynting vector.In honor of John Henry Poynting (1852-1914), English physicist; → theorem. Poynting-Robertson drag   کره‌ی ِ پوینتینگ-رابرتسون   kerre-ye Poynting-RobertsonFr.: traînée de Poynting-Robertson   A loss of → orbital angular momentum by tiny ring particles associated with their absorption and re-emission of → solar radiation. Also known as the → Poynting-Robertson effect (Ellis et al., 2007, Planetary Ring Systems, Springer).