An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A process in which an astronomical body loses mass mainly in the direction of its → equatorial regions, as opposed to → accretion.

From L. → ex- + crescere "to grow," → accretion.

An expanding → equatorial → disk or → torus of material ejected by a star. The phenomenon may result from a stellar → merger or an increase in its rate of → rotation or → stellar winds. Contrasted with → accretion disk.

→ excretion; → disk.

1) A short trip or outing to some place, usually for a special purpose and with the intention of a prompt return.
2) Physics: The displacement of a body or a point from a mean position or neutral value, as in an oscillation (Dictionary.com). → geomagnetic excursion.

From L. excursion- "a running forth, expedition," figuratively "an outset, opening," from excurrere "to run out," from → ex- "out" + currere "to run," → current.

Zocâr, literally "wander out, " from zo- "out," → ex-, + câr "to come and go, wander," related to car-, caridan "to psature, graze;" (Karingân) cârumé "excursion, walking around," (Sorxé) câqâle, (Sangesar, Semnân) ceqala "excursion;" Av. car- "to come and go, wander;" cf. Skt. car- "to move, walk, go;" Gk. pelomai "I move;" L. colere "to till, cultivate;" PIE root *k^welH- "to move, turn, wander."

The act of executing something; the state of being executed.

Verbal noun of → execute; → -tion.

1) Vigorous action; physical or mental effort.
2) The application or exercise of force, power, or faculties.

→ exert; → -tion.

1) The act or process of exhausting.
2) The state of being exhausted.
3) Extreme weakness or fatigue.
4) The total consumption of something (Dictionary.com).

→ exhaust; → -tion.

A natural → satellite orbiting an → extrasolar planet.

→ exo-; → moon.

1) General: The act or process of expanding; the state or quality of being expanded. → expansion of the Universe.
2) Math.: The process of expressing a quantity, or a quantity expressed, as a sum of a series of terms. For example the expression (2x - 1)(x + 3) can be expanded to: 2x² + 5x - 3. See also → binomial expansion.

Noun from → expand.

The receding of galaxies from one another at a speed proportional to their separation, as inferred by Edwin Hubble from the observed Doppler shift of distant galaxies. → Hubble constant describes the local rate of the expansion.

→ expansion; → universe.

A → scale factor that relates the size of the Universe R = R(t) at time t to the size of the Universe R₀ = R(t₀) at time t₀ by R = aR₀. The expansion parameter represents the history of expansion of the Universe.

→ expansion; → parameter.

Statistics: Same as → mathematical expectation, → expected value.

From L. expectare "to await, hope," from → ex- "thoroughly" + spectare "to look," from → specere "to look at," → -scope.

Bayusesš, verbal noun of bayusidan "to expect;" Mid.Pers. pyws- "to hope for, desire" (prefixed *pati-); O.Pers. vasiy "at will, greatly, utterly," vašna- "will, favor;" Av. vas- "to will, desire, wish, long for," vasəmi "I wish," vasna- "will, favor," ušti- "desire, wish, will," vasô, vasə "at one's will." This word is extant in several Mod.Pers. dialects, Tabari vessen "to wish, desire," Gilaki vâssan "to wish, desire," vâsti "desire," Kurd. wistin "to desire, wish," Lâri avessa "to desire," colloquial Tehrâni vâsé "for" (Mid.Pers. vasnâd "because"); cf. Skt. vaś- "to wish, want, desire," váśa- "wish, desire," vasēna "for, because;" Gk. ekon "voluntary;" PIE base *uek- "to wish."

1) The act or process of explaining.
2) A statement made to clarify something and make it understandable.

Verbal noun of → explain.

The most usual form of a function in which the dependent variable (written on the left hand side of the Same as → equality sign) is expressed directly in terms of independent variables written on the left (on the right hand side). See also → implicit function.

→ explicit; → function.

1) An act or instance of exploring or investigating; examination.
2. The investigation of unknown regions.
3) The process of searching for minerals by means of geological studies.
4) Medicine: An examination or investigation for diagnostic purposes, usually involving endoscopy or a surgical procedure.

Verbal noun of → explore.

The sudden and violent release of mechanical, chemical, or nuclear energy from a confined space which creates a heat wave that travels at → subsonic speeds. → detonation; → deflagration; → implosion.

Verbal noun of → explode.

Math.: A symbol or number placed above and after another symbol or number (called the base) to denote the power to which the latter is to be raised. Examples: n in the expresseion aⁿ; 3 in the expression 2³.

From L. exponentem, pr.p. of exponere "put forth, explain," from → ex- "forth" + ponere "to put, to place."

Nemâ, agent noun of nemudan "to show, display," from Mid.Pers. nimūdan, from ne- "down; into;" O.Pers./Av. ni- "down; into," → ni-, + mun, Av. māy- "to measure," → display.

Of or expressed by a mathematical → exponent. → exponential curve, → exponential equation, → exponential function.

→ exponent + -ial, variant of → -al.

A curve that represents an → exponential function.

→ exponential; → curve.

An equation in which unknowns appear as exponents. Examples: 2^{3x + 1} = 32.

→ exponential; → equation.

A function in the form of y = b^x defined for every → real number x, with positive base b > 1.

→ exponential; → function.