An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1965 Search : ion
  فرساختگی، فرسازش   
farsâxtegi, farsâzeš

Fr.: perfection   

The state or quality of being or becoming perfect.

perfect; → -tion.

  فرساختگرایی، فرساختگری   
farsâxtgerâyi, farsâxtgari

Fr.: perfectionisme   

1) Any of various doctrines holding that religious, moral, social, or political perfection is attainable.
2) A personal standard, attitude, or philosophy that demands perfection and rejects anything less (

perfection; → -ism.

  فرساختگرا، فرساختگر   
farsâxtgerâ, farsâxtgar

Fr.: perfectioniste   

1) A person who adheres to or believes in → perfectionism.
2) A person who demands perfection of himself, herself, or others (

perfection; → -ist.


Fr.: périlune   

The point in the orbit of a satellite around the Moon closest to the Moon; opposite of → apocynthion.

peri- + Gk. Cynthia "goddess of the Moon;" → Cynthian.

Pirâmâh, from pirâ-, → peri-, + mâhmoon.


Fr.: périhélie   

The nearest point to the Sun in an orbit around the Sun; opposite of → aphelion.

Perihelion, from L. perihelium, from → peri- + helios "sun," cognate with L. sol, Skt. surya, Av. hvar-, Mod.Pers. xor, hur, O.H.G. sunna, Ger. Sonne, E. sun; PIE *sawel- "sun".

Pirâhur, from pirâ-, → peri-, + hur "sun," as above;

perihelion advance
  پیشرفت ِ پیراهور   
pišraft-e pirâhur

Fr.: avance du périhélie   

advance of perihelion.

advance of perihelion.

perihelion distance
  اپست ِ پیراهوری   
apest-e pirâhuri

Fr.: distance au périhélie   

The distance between the → Sun and an → object in orbit around it when they are at their closest approach.

perihelion; → distance.

perihelion precession
  پیشایانِ پیراهوری   
pišÃ¢yân-e pirâhuri

Fr.: précession du périhélie   

advance of perihelion.

perihelion; → precession.

period-luminosity relation
  باز‌آنش ِ دوره-تابندگی   
bâzâneš-e dowré-tâbandegi

Fr.: relation période-luminosité   

A → correlation between the periods and luminosities of → Cepheid variable stars: Cepheids with longer periods are intrinsically more luminous than those with shorter periods. The relation was discovered by Henrietta Leavitt in 1912 when studying Cepheids in the → Small Magellanic Cloud. Once the period of a Cepheid variable is determined from observations, the period-luminosity relation can be used to derive its luminosity. Since luminosity is a function of → distance, the distance can then be calculated with the luminosity. The period-luminosity relation is an invaluable tool for the measurements of distances out to the nearest galaxies and thus for studying the structure of our own Galaxy and of the Universe.

period; → luminosity; → relation.

period-mean density relation
  باز‌آنش ِ دوره-چگالی ِ میانگین   
bâzâneš-e dowré-cagâli-ye miyângin

Fr.: relation période-densité moyenne   

A relation that gives a rough estimate of the oscillation period of a → pulsating star as a function of its mean density. This relation is obtained by considering how long it would take a sound wave to travel across the diameter of a model star: Π ≅ (3π/2γGρ)1/2, where ρ is the mean density, γ the ratio of → specific heats (Cp/Cv), and G the → gravitational constant. This relation shows that the pulsation period of a star is inversely proportional to the square root of its mean density. And this is the reason why the pulsation periods decrease along the → instability strip from the luminous, very tenuous → supergiants to the faint, very dense → white dwarfs.

period; → mean; → density; → relation.

periodic function
  کریای ِ دوره‌ای   
karyâ-ye dowreyi

Fr.: fonction périodique   

A function f(x) if for all x, f(x + P) = f(x), where P is a positive constant. The least value of P > 0 is called the period of f(x).

periodic; → function.

periodic motion
  جنبش ِ دوره‌ای   
jonbeš-e dowreyi

Fr.: mouvement périodique   

Any motion that recurs in identical forms at equal intervals of time.

periodic; → motion.

peripheral vision
  دید ِ پیرابَری   
did-e pirâbari

Fr.: vision périphérique   

In optics, the ability to see over large angles of view.

peripheral; → vision.


Fr.: permission   

The act of permitting. Authorization granted to do something.

verbal noun of → permit; → -tion.

permitted transition
  گذرش ِ پرزامیده   
gozareš-e parzâmidé

Fr.: transition permise   

A transition between two quantum mechanical states that does not violate the quantum mechanical selection rules.

permitted; → transition.

  پرموتش، جایگشت   
permuteš, jâygašt

Fr.: permutation   

Math.: A rearrangement of the elements of a set in a particular order. The number of permutations of n objects is equal to n! (→ factorial n). For example, there are 24 permutations of letters A, B, C, and D (4! = 1 × 2 × 3 × 4). The number of permutations of n objects taken r at a time is denoted by nPr and equals n! / (n - r)!. For example, the number of permutation of A, B, C, and D taken two at a time is 12. If n objects are of k different kinds, with r1 alike of one kind, permutations of n objects equals n! / r1! r2! ... rk!, where r1 + r2 + ... rk = n.

Verbal noun of → permute.

Permuteš, verbal noun of → permute.
Jâygašt , from "place" (from Mid.Pers. giyag "place;" O.Pers. ā-vahana- "place, village;" Av. vah- "to dwell, stay," vanhaiti "he dwells, stays;" Skt. vásati "he dwells;" Gk. aesa (nukta) "to pass (the night);" Ossetic wat "room; bed; place;" Tokharian B wäs- "to stay, wait;" PIE base ues- "to stay, live, spend the night") + gašt past tense of gaštan, gardidan "to turn, to change" (Mid.Pers. vartitan; Av. varət- "to turn, revolve;" Skt. vrt- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wer- "to turn, bend").

perpetual motion
  جنبش ِ همیشگی   
jonbeš-e hamišegi

Fr.: mouvement perpétuel   

The motion of a hypothetical machine which, once set in motion, will go on for ever without any losses due to → friction or other forms of → dissipation of energy and without receiving any external energy.

perpetual; → motion.

personal equation
  هموگش ِ تنومی   
hamugeš-e tanumi

Fr.: équation personnelle   

A systematic observational error due to the characteristics of the observer.

Personal, adj. of → person; → equation.


Fr.: personnification   

1) The attribution of human nature or character to animals, inanimate objects, or abstract notions, especially as a rhetorical figure.
2) The representation of a thing or abstraction in the form of a person, as in art.
3) The person or thing embodying a quality or the like; an embodiment or incarnation (

Verbal noun of → personify.


Fr.: perturbation   

1) Any departure introduced into a steady state of a system. The magnitude is often assumed to be small so that the resulting terms in the dependent variables may be neglected. The term "perturbation" is therefore sometimes used as synonymous with "small perturbation."
2) Gravitational effect of a third body that causes an alteration in the orbit of a body going around its primary.
See also: → linear perturbation theory, → method of small perturbationsn → perturbation equation, → perturbation method, → primordial curvature perturbation, → scalar perturbation, → secular perturbation, → tensor perturbation, → vector perturbation.

Verbal noun of → perturb.

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