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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

   Homepage   
   


A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

<< < D l dar dat de deb dec dec dec def def dei dem den dep det deu dew Die dif dif dim dip dir dis dis dis dis div dom dou dow dro dus dwa dyn > >>

Number of Results: 699
dipole radiation
  تابش ِ دوقطبه   
tâbeš-e doqotbé

Fr.: rayonnement dipolaire   

The electromagnetic radiation produced by an oscillating → electric dipole or → magnetic dipole.

dipole; → radiation.

diproton
  دیپروتون   
diproton

Fr.: diproton   

An → isotope of → helium that consists of two → protons, without any → neutrons. It is extremely → unstable.

di-; → proton.

Dirac
  دیراک   
Dirac

Fr.: Dirac   

Paul A. M. Dirac (1902-1984), English theoretical → physicist, one of the founders of → quantum mechanics and → quantum electrodynamics, Nobel Prize for Physics in 1933. → Dirac annihilation, → Dirac equation, → Dirac function, → Dirac's constant, → Fermi-Dirac statistics .

Dirac annihilation
  نابودی ِ دیراک   
nâbudi-ye Dirac

Fr.: annihilation de Dirac   

Same as → pair annihilation.

Dirac; → annihilation.

Dirac equation
  هموگش ِ دیراک   
hamugeš-e Dirâk

Fr.: équation de Dirac   

The equation that describes the behavior of an electron in a way that combines the requirements of quantum mechanics with the requirements of relativity.

Dirac; → equation.

Dirac function
  کریای ِ دیراک   
karyâ-ye Dirâk

Fr.: fonction de Dirac   

A function of x defined as being zero for all values of x other than x = x0 and having the definite integral from x = -∞ to x = +∞ equal to unity.

Dirac; → function

Dirac's constant
  پایای ِ دیراک   
pâyâ-ye Dirac

Fr.: constante de Dirac   

The → Planck's constant divided by 2π and denoted ħ, pronounced h-bar. Also called → reduced Planck's constant.

Dirac; → constant.

direct
  ۱) راست، سرراست؛ ۲) راشتیدن   
1) râst (#), sarrâst (#); 2) râštidan

Fr.: 1) direct; 2) diriger   

1a) Proceeding in a straight course or line without deviation or interruption.
1b) Math.: Varying in the same manner as another quantity, especially increasing if another quantity increases or decreasing if it decreases.
1c) Astro.: Designating west-to-east motion of a planet in the same direction as the Sun's movement against the stars.
2) To administer; manage; supervise; to serve as a director in the performance or production of.

From L. directus "straight," p.p. of dirigere "set straight," from → dis- "apart" + regere "to guide;" cognate with Pers. râst, as explained below.

Râst "right, straight" (râšt in afrâštan); Mid.Pers. râst; O.Pers. rāsta- "straight, true," rās- "to be right, straight, true," rād- "to prepare;" Av. rāz- "to direct, put in line, set," razišta- "straightest, most correct," erezu- "correct, straight," rāzayeiti "directs," razan- "order;" Skt. raj- "to direct, stretch," rjuyant- "walking straight;" Gk. orektos "stretched out;" L. regere "to lead straight, guide, rule," p.p. rectus "right, straight;" Ger. recht; E. right; PIE base *reg- "right, just; to move in a straight line."
Sarrâst, from sar here an intensive element meaning "side," originally "head" (Mid.Pers. sar; Av. sarah- "head;" Skt. siras- "head;" Gk. kara "head," keras "horn;" Mod.Pers. sarun "horn;" L. cerebrum "brain;" PIE *ker- "head, horn") + râst, as above.
Râštidan, infinitive from râšt, variant râst "direct."

direct correlation
  هم‌باز‌آنش ِ سرراست   
hambâzâneš-e sarrâst

Fr.: corrélation directe   

A correlation between two variables such that as one variable becomes large, the other also becomes large, and vice versa. The correlation coefficient is between 0 and +1. Also called positive correlation.

direct; → correlation.

direct current (DC)
  جریان ِ سرراست   
jarayân-e sarrâst

Fr.: courant continu   

An → electric current which flows in one direction only and which is substantially constant in magnitude. Virtually all electronic and computer hardware needs direct current to function. → Alternating current can be converted to direct current by means of a power supply consisting of a → transformer.

direct; → current.

direct motion
  جنبش ِ فرارو، ~ سرراست   
jonb eš-e farârow, ~ sarrâst

Fr.: mouvement direct   

The motion of a solar system body from West to East across the sky against the background stars. It is the "normal" direction of motion within the solar system. For rotating or orbiting solar system objects it is anti-clockwise as seen from above the solar system in the direction of the North Pole. The same as → prograde motion. See also → retrograde motion.

direct; → motion.

directed edge
  لبه‌ی ِ سودار   
labe-ye sudâr

Fr.: graphe orienté   

In → graph theory, an edge where endpoints are distinguished; one is the head and the other is the tail. A directed edge is specified as an ordered pair of → vertices, u, v and is denoted by (u, v) or uv.

directed; → edge.

directed graph
  نگاره‌ی ِ سودار   
negâre-ye sudâr

Fr.: graphe orienté   

In → graph theory, a graph with → directed edges. Also calle → digraph.

directed; → graph.

directed path
  په ِ سودار   
pah-e sudâr

Fr.: chemin orienté   

In a → directed graph, a path in which all → edges are oriented in the same direction.

directed; → edge.

direction
  راستا، سو؛ ۲) راشتاری   
1) râstâ, su (#); 2) râštâri

Fr.: direction   

1) A position to which motion or another position is referred.
2) The act or an instance of directing.

M.E. direccioun, from M.Fr., from L. direction-, stem of directio "arranging in line, straightening," → direct.

1) Râstâ, from directdirect + dimension suffix; su, from Mid.Pers. sôk "side."
2) Râštâri, noun from râštârdirector + suffix -i.

direction angle
  زاویه‌ی ِ راستا   
zâviye-ye râstâ

Fr.: angle de direction   

An angle made by a given vector and a coordinate axis.
The angle between the North and a chosen direction.

direct; → angle.

director
  راشتار   
râštâr

Fr.: directeur   

A person who directs a project, a group, a production.

From → direct + -tor a suffix found in loanwords from L., forming personal agent nouns from verbs.

Râštâr, from râšt- stem of râštidandirect + -âr suffix of agent noun (as in parastâr "nurse").

Dirichlet condition
  بوتار ِ دیریکله   
butâr-e Dirichlet

Fr.: condition de Dirichlet   

One of the following conditions for a → Fourier series to converge:
1) The function f(x) is defined and single valued, except possibly at a finite number of points in the interval -π, +π.
2) f(x) has a period of 2π.
3) f(x) and f'(x) are → piecewise continuous functions on -π, +π.
Then, the Fourier series converges to:
(a) f(x) if x is a point of continuity.
(b) (f(x + 0) + f(x - 0))/2, if x is a point of discontinuity.

Named after Peter Gustav Lejeune Dirichlet (1805-1859), German mathematician who made valuable contributions to → number theory, → analysis, and → mechanics; → condition.

dirt
  چرک   
cerk (#)

Fr.: saleté   

A substance, such as mud or dust, that soils someone or something (OxfordDictionaries.com)

Metathesis of M.E. drit, drytt "mud, dirt, dung," from O.N. drit, cognate with O.E. dritan.

Cerk "dirt, filth."

dirty
  چرکین   
cerkin (#)

Fr.: sal   

Covered or marked with an unclean substance. → dirty ice, → dirty iceball model.

dirt + suffix -y.

<< < D l dar dat de deb dec dec dec def def dei dem den dep det deu dew Die dif dif dim dip dir dis dis dis dis div dom dou dow dro dus dwa dyn > >>