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

The extent of → coherence of an → electromagnetic wave, as indicated by a → dimensionless number. Since interference takes place when waves are → coherent, using a → Young's experiment, the degree of coherence is measured from the → fringe  → visibility, V. It is defined as the ratio V = (I_max - I_min) / (I_max + I_min), where I_max is the intensity at a maximum of the → interference pattern, and I_min is the intensity at a minimum of the interference pattern. The electromagnetic wave is considered to be highly coherent when the degree of coherence is about 1, incoherent for nearly zero values, and partially coherent for values between 0 and 1.

→ degree; → coherence.

Of a → mechanical system, the number of → independent variables needed to describe its configuration.

→ degree; → freedom.

The number of electrons a neutral atom has lost in an ionizing physical process (radiation, shock, collision). In spectroscopy, the degree of ionization is indicated by a Roman numeral following the symbol for the element. A neutral atom is indicated by the Roman numeral I, a singly ionized atom, one which has lost one electron, is indicated by II, and so on. Thus O VI indicates an oxygen atom which has lost five electrons.

→ degree; → ionization.

The ratio of the intensity of polarized portion of light to the total intensity at a point in the beam.

→ degree; → polarization.

Statics: The → energy that must be expended to permanently disturb a specific state of → equilibrium of a body.

→ degree; → stability.

The → number of → edges incident on the → vertex.

→ degree; → vertex.

The act or process or an instance of dehumanizing.

Verbal noun of → dehumanize.

To deprive of → human qualities or personality.

→ de-; → dehumanize.

The smaller and outermost of Mars' two satellites. It measures 12.6 km in size, and orbits Mars every 30.2 hours at a distance of about 23,500 km. It was discovered by the American astronomer Asaph Hall in 1877.

In Gk. mythology, Deimos, meaning "fear, terror," is one of the sons of Ares (Mars) and Aphrodite (Venus).

Chemistry: A process in which all charged species are removed from a solution.
The return of an ionized gas to its non-ionized state after the ionizing source has been removed.

From → de- + → ionization.

1) Belief in the existence of a → God on the evidence of → reason and → nature only, with rejection of supernatural revelation (distinguished from → theism).
2) Belief in a God who created the world but has since remained indifferent to it (Dictionary.com).

From Fr. déisme, from L. de(us) "god," → deity, + → -ism.

Dâdâr-bâvari, from dâdâr "creator," → author, + bâvari, → ism; izad-bâvari, from izad "god," → deity.

A person who believes in → deism.

→ deism; → -ist

1) A god or goddess.
2) Divine character or nature, especially that of the Supreme Being; divinity (Dictionary.com).

M.E. deite, from O.Fr., from L.L. deitat- (nominative deitas), from L. dei- (combining form of deus "god") + -tat- "-ty," formed after L. divinitas "divinity."

Izad "god;" from Mid.Pers. yazêt "god; angel," izišn "performance of the religious rites, worship," yašt "worship, religious ceremony," yaštan "to venerate, to perform the religious ceremony;" O.Pers. yad- "to worship;" Av. yaz- "to sacrifice, worship, venerate," yazata- "deities," yasna- "religious rite" (Mod.Pers. jašn "feast"); Proto-Ir. *iaz- "to sacrifice, worship, venerate."

In → vector calculus, a vector → partial derivative represented by the symbol → nabla and defined in three dimensions to be:
∇ = (∂/∂x)i + (∂/∂y)j + (∂/∂z)k.
It appears in the operations → gradient: ∇f, → divergence: ∇ . E, → curl: ∇ x E, and → Laplacian: ∇ . ∇f = ∇²f.

From Gk. alphabet letter delta.

The amount of time by which an event is retarded.

From O.Fr. délaier, from dé-→ de- "away, from" + laiier, from laiss(i)er "to leave," from L. laxare "to loosen, release, set free."

Derang, from Mid.Pers. dirang, drang "delay, lateness; long, lasting," Av. drənj- "to fix, fasten, hold," Proto-Iranian *dra(n)j- "to fix, fasten, hold."

Same as → delay.

→ delay; → time.

Neutrons resulting from nuclear fission which are emitted with a measurable time delay. Delayed neutrons are responsible for the ability to control the rate at which power can rise in a reactor. → prompt neutrons.

Delayed, p.p. of the verbal form of → delay; → neutron.

A mechanism predicted by theoretical models of → supernova explosion that operates after the → supernova shock fails to deliver a → prompt supernova explosion. The delayed supernova explosion mechanism assumes that a few tenth of a second after the → iron core collapse, the supernova shock is stalled due to energy dissipation. The material between the → protoneutron star and the stalled shock is mainly disintegrated into neutrons and protons due to the high temperatures (a few MeV) in this region. As the → neutrinos coming from the protoneutron star run through this material, a fraction of the neutrinos are captured by the → nucleons, and their energy is deposited in the material. As a result, the material behind the shock is heated by the neutrinos. If this neutrino heating is efficient enough, the stalled shock can be reinvigorated to bring about a supernova explosion.

→ delay; → supernova; → explosion.

To strike out or remove (something written or printed); cancel; erase.

L. deletus, p.p. of delere "destroy, blot out, efface," from delevi, fro delinere "to erase by smudging," from → de- "from, away" + linere "to smear, wipe."

Rušidan, from Kurd. rušê "to be wiped off through rubbing;" cf. Av. fra.uruxti- "destruction;" Wakhi riz-, rəz-/rəzd- "to tear apart, rip up a seam;" Yaghnobi ruc/ructa, rušta "to shave off the skin, skin off;" Proto-Ir. *rauj- "to break, bust" (Cheung 2007).

1) An act or instance of deleting. The state of being deleted. A deleted word, passage, etc.
2) Genetics: A type of chromosomal aberration in which a segment of the chromosome is removed or lost (Dictionary.com).

Verbal noun from → delete.