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

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 36 Search : mean
 arithmetic mean   میانگین ِ حسابی   miyângin hesâbi (#)Fr.: moyenne arithmétique   Of n numbers a1, a2, ..., an, the quantity defined as: (a1 + a2 + ... + an)/n.→ arithmetic; → mean. geometric mean   میانگین ِ هندسی   miyângin-e hendesi (#)Fr.: moyenne géométrique   The middle term in a → geometric progression. Of two terms, the geometric mean is the square root of their product. For example, the geometric mean of 4 and 9 is ± 6. For a series of n terms, it is expressed as: (a1.a2. ... .an)1/n.→ geometric; → mean. Greenwich Mean Sidereal Time (GMST)   زمان ِ اختری ِ میانگین ِ گرینویچ   zamân-e axtari-ye miyângin-e GreenwichFr.: temps sidéral moyen de Greenwich   The → sidereal time related to the angle between the → prime meridian and the → mean vernal equinox, measured in the plane of the equator.→ mean; → Greenwich Meridian; → sidereal; → time. harmonic mean   میانگین ِ هماهنگ   miyângin-e hamâhangFr.: moyenne harmonique   A number whose reciprocal is the → arithmetic mean of the reciprocals of a set of numbers. Denoted by H, it may be written in the discrete case for n quantities x1, ..., xn, as: 1/H = (1/n) Σ(1/xi), summing from i = 1 to n. For example, the harmonic mean between 3 and 4 is 24/7 (reciprocal of 3: 1/3, reciprocal of 4: 1/4, arithmetic mean between them 7/24). The harmonic mean applies more accurately to certain situations involving rates. For example, if a car travels a certain distance at a speed speed 60 km/h and then the same distance again at a speed 40 km/h, then its average speed is the harmonic mean of 48 km/h, and its total travel time is the same as if it had traveled the whole distance at that average speed. However, if the car travels for a certain amount of time at a speed v and then the same amount of time at a speed u, then its average speed is the arithmetic mean of v and u, which in the above example is 50 km/h.→ harmonic; → mean. mean   ۱) میانگین؛ ۲) چماردن   1) miyângin (#); 2) cemârdanFr.: 1) moyenne; 2) signifier, vouloir dire   1a) General: A quantity having a value intermediate between the values of other quantities; an average. 1b) → arithmetic mean. 1c) → geometric mean. 1d) → harmonic mean. 1e) → weighted mean. 1f) → root mean square. 2) To have as its sense or signification; signify.1) From O.Fr. meien, from L. medianus "of or that is in the middle," → median. 2) Verb of → meaning.1) Miyângin "the middle; middle-sized; the middle pearl in a string," from miyân, → middle, + -gin a suffix forming adjectives of possession. 2) → meaning. mean anomaly   ناسانی ِ میانگین   nâsâni-ye miyânginFr.: anomalie moyenne   The angle between the periapsis of an orbit and the position of a hypothetical body that orbits in the same period as the real one but at a constant mean angular velocity.→ mean; → anomaly. mean catalog place   جای ِ میانگین ِ کاتالوگی   jâ-ye miyângin-e kâtâlogiFr.: position catalogue moyenne   That point on the → celestial sphere at which an object would be seen from the solar system → barycenter affected by the → e-terms → aberration.→ catalog; → mean; → place. mean daily motion   جنبش ِ روزانه‌ی ِ میانگین   jenbeš-e ruzâne-ye miyângin (#)Fr.: mouvement diurne moyen   The average movement of a body along its orbit in one day, usually expressed in degrees.→ mean; → diurnal; → motion. mean element   بن‌پار ِ میانگین   bonpâr-e miyânginFr.: élément moyen   An element of an adopted reference orbit that approximates the actual, perturbed orbit. Mean elements may serve as the basis for calculating perturbations.→ mean; → element. mean equator   هموگار ِ میانگین   hamugâr-e miyânginFr.: équateur moyen   The orientation the Earth's equator would have if the nutation was subtracted.→ mean; → equator. mean equinox   هموگان ِ میانگین   hamugân-e miyânginFr.: équinoxe moyen   A fictitious equinox whose position is that of the vernal equinox at a particular epoch with the effect of nutation removed.→ mean; → equinox. mean free path   پویش ِ آزاد ِ میانگین   puyeš-e âzâd-e miyângin (#)Fr.: libre parcours moyen   The mean distance which a particle moves between two successive collisions with other particles of the medium. Mean free path is inversely proportional to the number of particles per cm3 (n), and the collision → cross section (σ). In the case of a gas with molecules having a diameter of d, the cross section is equal to the area of a circle of radius d, i.e. σ = πd2, and the mean free path is given by: l = 1/(nσ). Taking into account the relative velocity distribution of the colliding molecules, l = 1/(√2 . nσ). For a gas at one atmosphere pressure and room temperature, the average distance between molecules is roughly 3.5 × 10-7 cm, that is some 35 times the diameter of a molecule. Taking the gas density n = 2.4 × 1014 molecules cm-3, and a typical diameter d = 2 × 10-8 cm for a molecule, the mean free path is 3.3 × 10-5 cm. This means that the average distance between collisions is about 95 times the average distance between molecules.→ mean; → free; → path.Puyeš, verbal noun of puyidan "to run, trot; wander," from Mid.Pers. pôy-, pwd- "to run;" cf. Gk. speudein "to hasten;" Lith. spudinti; âzâd, → free; miyângin, → mean. mean life   زیست ِ میانگین   zist-e miyânginFr.: vie moyenne   The average amount of time an unstable radioisotope exists before it decays, It is equal to 1.44 times the half-life.→ mean; → life. mean molecular weight   وزن ِ مولکولی ِ میانگین   vazn-e molekuli-ye miyângin (#)Fr.: poids moléculaire moyen   The total atomic or molecular weight divided by the total number of particles. For instance, the mean molecular weight of a plasma of pure ionized 4He would be 4 (the atomic mass number) divided by 3, the total number of particles (1 nucleus plus 2 electrons), i.e. 4/3.→ mean; → molecular; → weight. mean moon   ماه ِ میانگین   mâh-e miyângin (#)Fr.: lune moyenne   A fictitious Moon that has the same average motion as the true Moon but that is not subject to any gravitational perturbations by other bodies.→ mean; → moon. mean motion   جنبش ِ میانگین   jonbeš-e miyângin (#)Fr.: mouvement moyen   The average angular velocity of a satellite in an elliptical orbit.→ mean; → motion. mean parallax   دیدگشت ِ میانگین   didgašt-e miyânginFr.: parallaxe moyenne   The parallax, derived by means of statistical studies of brightness and motions, for a large group of stars whose individual parallaxes cannot be measured.→ mean; → parallax. mean place   جای ِ میانگین   jâ-ye miyânginFr.: position moyenne   An object's celestial position as determined for a given mean equator and equinox. → mean position.→ mean; → place. mean pole   قطب ِ میانگین   qotb-e miyânginFr.: pôle moyen   The direction of the Earth's axis at a particular epoch if the nutation is ignored.→ mean; → pole. mean position   نهش ِ میانگین   neheš-e miyânginFr.: position moyenne   Same as → mean place.→ mean; → position.

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