An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 3106 Search : on
hydrocarbon
  هیدروکربون   
hidrokarbon (#)

Fr.: hydrocarbure   

Any of a class of compounds containing only → hydrogen and → carbon. Hydrocarbons are organic compounds found in coal, petroleum, natural gas, and plant life. They are used as fuels, solvents, and as raw materials for numerous products such as dyes, pesticides, and plastics. Petroleum is a mixture of several hydrocarbons.

hydro- + → carbon.

hydrodynamic equation
  هموگش ِ هیدروتوانیک   
hamugeš-e hirdrotavânik

Fr.: équation hydrodynamique   

Fluid mechanics: A → partial differential equation which describes the motion of an element of fluid subjected to different forces such as pressure, gravity, and frictions.

hydrodynamic; → equation.

hydrogen bond
  بند ِ هیدروژنی   
band-e hidroženi

Fr.: liaison hydrogène   

The attractive force between the hydrogen attached to an electronegative atom of one molecule and an electronegative atom of a different molecule. Usually the electronegative atom is oxygen, nitrogen, or fluorine, which has a partial negative charge. The hydrogen then has the partial positive charge.

hydrogen; → bond.

hydrogen fusion
  ایوش ِ هیدروژن   
iveš-e hidrožen

Fr.: fusion de l'hydrogène   

A → nuclear reaction where hydrogen (H) nuclei combine to form helium (4He) nuclei. Same as the → proton-proton chain.

hydrogen; → fusion.

hydrogen ion
  هیدرون، یون ِ هیدروژن   
hidron, yon-e hidrož

Fr.: hydron, ion hydrogène   

Chemistry: The → positively charged hydrogen atom, H+, formed by removal of the orbital electron. Same as → proton.

hydrogen; → ion.

hydrogenation
  هیدروژنش   
hidroženeš

Fr.: hydrogénisation   

The process of combining or exposing to → hydrogen.

hydron
  هیدرون   
hidron (#)

Fr.: hydron   

The general name for the atomic hydrogen → cation H+.

hydro-; → -on.

hydronium
  هیدرونیوم   
hidroniom

Fr.: hydronium   

A → water, → molecule with an additional hydrogen ion (H3O+). Also called hydronium ion. Hydronium is an abundant molecular ion in the interstellar diffuse and dense molecular clouds (→ Sagittarius B2, → Orion molecular cloud OMC-1) as well as the plasma tails of → comets (→ Halley, → Hale-Bopp).

From hydr-, → hydro- + -onium a suffix used in the names of complex cations, extrcated from ammonium "ionized ammonia" (NH4+).

hydrostatic equation
  هموگش ِ هیدر-ایستاییک   
hamugeš-e hidristâik

Fr.: équation hydrostatique   

The equation describing the → hydrostatic equilibrium in a star, expressed as: dP/dr = -GMρ/r2, where P and M are the mass and pressure of a spherical shell with thickness dr at some distance r around the center of the star, ρ is the density of the gas, and G the → gravitational constant.

hydrostatic; → equation.

hyperbolic function
  کریایِ هذلولی   
karyâ-ye hozluli

Fr.: fonction hyperbolique   

Any of the six functions sinh, cosh, tanh, coth, csch, and sech that are related to the → hyperbola in the same way the → trigonometric functions relate to the → circle. Many of the formulae satisfied by the hyperbolic functions are similar to corresponding formulae for the trigonometric functions, except for + and - signs. For example: cosh2x - sinh2x = 1. See also: → hyperbolic cosine, → hyperbolic sine. Hyperbolic functions were first introduced by the Swiss mathematician Johann Heinrich Lambert (1728-1777).

hyperbolic; → function.

hyperfine transition
  گذرش ِ اَبَرنازک   
gozareš-e abar-nâzok

Fr.: transition hyperfine   

An → atomic transition involving a → hyperfine structure.

hyperfine; → transition.

Hyperion (Saturn VII)
  هوپریون   
Huperion (#)

Fr.: Hypérion   

The sixteenth of → Saturn's known → natural satellites. It is shaped like a potato with dimensions of 410 x 260 x 220 km and has a bizarre porous, sponge-like appearance. Many of the sponge holes or craters have bright walls, which suggests an abundance of → water  → ice. The crater floors are mostly the areas of the lowest → albedo and greatest red coloration. This may be because the average temperature of roughly -180 °C might be close enough to a temperature that would cause → volatiles to → sublimate, leaving the darker materials accumulated on the crater floors. Hyperion is one of the largest bodies in the → Solar System known to be so irregular. Its density is so low that it might house a vast system of caverns inside. Hyperion rotates chaotically and revolves around Saturn at a mean distance of 1,481,100 km. It was discovered by two astronomers independently in 1848, the American William C. Bond (1789-1859) and the British William Lassell (1799-1880).

Hyperion, in Gk. mythology was the Titan god of light, one of the sons of Ouranos (Heaven) and Gaia (Earth), and the father of the lights of heaven, Eos the Dawn, Helios the Sun, and Selene the Moon.

hyperon
  هیپرون   
hiperon (#)

Fr.: hypéron   

An unstable elementary particles, belonging to the class called → baryons, which have greater mass than the neutron but very short lives (10-8 to 10-10 seconds).

From → hyper- + → -on a suffix used in the names of elementary particles (gluon; meson; neutron; graviton, and so on).

hypersonic
  هیپرصدایی   
hipersedâyi

Fr.: hypersonique   

In aerodynamics, adjective used to describe a → sound speed in excess of Mach 5. See also → supersonic.

Hypersonic, from → hyper- + → sonic.

ice accretion
  فربال ِ یخ   
farbâl-e yax

Fr.: accrétion de glace   

Meteo.: The process by which a layer of ice builds up on solid objects that are exposed to freezing precipitation or to supercooled fog or cloud droplets.

ice; → accretion.

icon
  زدیش   
zodiš

Fr.: icone   

1) An image; a representation.
2) A representation or picture of a sacred or sanctified Christian personage, traditionally used and venerated in the Eastern Church.
3) A person or thing regarded as a symbol of a belief, nation, community, or cultural movement.
4) Computers: A pictorial representation of a facility available on a computer system, that enables the facility to be activated by means of a screen cursor rather than by a textual instruction (TheFreeDictionary.com).

From Gk. eikon "likeness, image, portrait; a semblance;" in philosophy, "an image in the mind," related to eikenai "be like, look like," from PIE *weik- "to be like."

Zodiš, variant of Mid.Pers. uzdês "icon; image; idol," from uz-, → ex-, + dês, Av. daēs- "to show;" cognate with Gk. deiknumai "to show;" L. dicere "to utter, say, proclaim;" N.H.G. zeigen "to say;" O.E. têon "to annoince;" PIE *deik- "to show, point out; announce."

identification
  ایدانش   
idâneš

Fr.: identification   

1) An act or instance of identifying; the state of being identified.
2) Psychology: The process of associating the self closely with other persons and assuming their characteristics or views unconsciously or partially so.
3) In psychological theories, a phase of recognition, the way in which the child's personality is formed by modeling it on a chosen parent.

Verbal noun of → identify.

Idâneš, verbal noun of idânidanidentify.

identification of lines
  ایدانش ِ خطها   
idâneš-e xatthâ

Fr.: identification de raies   

Recognizing the lines in the spectrum of a star, nebula, galaxy, etc. using a calibration template.

identification; → line.

identity function
  کریای ِ ایدانی   
karyâ-ye idâni

Fr.: fonction d'identité   

Math.: Any function f for which f(x) = x for all x in the domain of definition.

identity; → function.

if and only if (iff)
  اگر و ایواز اگر، ~ ~ تنها ~   
agar va ivâz agar, ~ ~ tanhâ ~

Fr.: si et seulement si   

Logic, Math.: An → expression indicating that two → statements so connected are → necessary and sufficient conditions for one another. The corresponding logical symbols usually used are: ↔, ⇔, ≡, and iff.

if; → and; → only.

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