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

1) The angle by which a light ray is curved by the gravitational field of a massive body. Einstein's general relativity predicts that a light ray which tangentially grazes the surface of the Sun is deflected by 1''.7. This result was confirmed in 1919 when the apparent angular shift of stars close to the limb of the Sun was measured during a total solar eclipse.
2) In a cathode-ray tube, the angle through which the beam is bent, vertically, horizontally, or diagonally.

→ deflection; → angle.

The bending of a light ray under the gravitational effect of a massive body. → deflection angle.

→ deflection; → light.

To cause to deviate from accurate focus.

→ vâ- + → focus.

1) To undergo → deformation.
2) To change the form or shape of. → deformable, → deformed, → deformation.

From O.Fr. déformer, from L. deformare "to disfigure," from → de- + → form.

Vâdisidan, vâdisândan infinitive from vâdis, from vâ-, → de-, + dis, → form.

Capable of being → deformed. → deformable mirror

→ deform + → -able.

A very thin mirror whose shape can be changed by the force applied by many small pistons behind the mirror. Such a mirror is used in the → adaptive optics technique to correct the → wavefront affected by the → atmospheric turbulence. See also → tip-tilt mirror.

→ deformable; → mirror.

Altering in the size or shape of a body. See also → deformable.

Verbal noun of → deform.

Having the → form → changed.

Past participle of → deform.

1) No longer in effect or use; not operating or functioning.
2) No longer in existence; dead; extinct.

M.E., from O.Fr. defunct or directly from L defunctus "dead," literally "off-duty," from p.p. of defungi "to discharge, finish," from → de- "off, completely" + fungi "perform or discharge duty," from PIE root *bheug- "to enjoy" (cognates: Latin fructus).

Nâkâr, "disabled" (Dehxodâ), leterally "not working," from negation prefix nâ-, → un-, + kâr, kardan, → work

A comet that has lost its ability to emit dust and gas and no longer displays the classic cometary features of a nebulous coma and a tail, or a destroyed comet. Comet Pigott The asteroid (944) Hidalgo is considered by some to be a defunct comet because of its unusual orbit. Another case is the asteroid Phaethon.

→ defunct; → comet.

The process of producing a quantifiable result in a → fuzzy logic system, given → fuzzy sets and corresponding → membership functions. Defuzzification is the last step in a fuzzy logic system. After → fuzzy inferencing, the overall result is a → fuzzy value. This result should be defuzzified to obtain a final → crisp value.

Verbal noun of → defuzzify; → -tion.

To transform a → fuzzy set to a → crisp set in a → fuzzy logic system.

→ de-; → fuzzy; → -fy.

1) General: Degenerate state or character. Reverting to an earlier, simpler, state.
2) Math.: Limiting case in which a class of object changes its nature so as to belong to another, usually simpler, class.
3) Physics: In quatum mechanics, the condition in which two or more different → wave functions of a system correspond to the same energy. In the case of atomic energy levels, the degeneracy can be removed, for example, by applying an electric field to the atom.
State or charcater of → degenerate matter.

From degener(ate), → degenerate, + -acy suffix of nouns of quality and state.

Vâgeni, from vâgen, → degenerate, + noun suffix -i.

Pressure in a degenerate electron or neutron gas. → degenerate matter.

→ degeneracy; → pressure.

Characterized by or associated with → degeneracy.

L. degeneratus, p.p. of degenerare "depart from one's kind, fall from ancestral quality," from → de- + gener-, stem of genus "race, stock, kind," gignere "to beget," cf. with Gk. genos "race, kind," gonos "birth, offspring," from PIE base *gen-/*gon-/*gn- "to produce, beget, be born," cf. Av. zan- "to bear, give birth to a child, be born," infinitive zazāite, zāta- "born," zana- "race" (in sruuô.zana- "belonging to the race of the horned ones"), O.Pers. zana- "tribe" (in paru-zana- "consisting of many tribes"), Skt. janati "begets, bears," jana- "creature, human being, race, tribe, people."

Vâgen, from vâ-, → de-, + gen "kind," (as in hamgen "of the same kind, like each other; friend, partner," from ham- "together," → com- + gen "kind," O.Pers./Av. zana- "race; tribe," cognate with L. genus, as above). Alternatively, gen may be a variant of Mid./Mod.Pers. gôn/gun "kind, type; manner; color, skin color," from Av. gaona- "hair, hair color, color."

Same as → white dwarf.

→ degenerate; → dwarf.

Highly compressed matter in which the normal atomic structure has broken down and which, because of quantum-mechanical effects, exerts a pressure that is independent of temperature. Bodies with masses less than → Chandrasekhar's limit (1.4 solar masses) are supported by electron → degeneracy pressure and have densities of about 10⁶ kg/m³. In collapsed stars of mass above 1.4 solar masses, gravity will overwhelm electron degeneracy and further collapse ensues. Electrons combine with protons to form neutrons, so producing a → neutron star. Because neutrons, like electrons, are → fermions and therefore subject to the → Pauli exclusion principle, at high enough densities, about 10¹⁴ kg/m³, neutron degeneracy pressure prevents further collapse of the star. For masses larger than 2-3 solar masses, even neutron degeneracy cannot prevent further collapse, and a → black hole is formed.

→ degenerate; → matter.

1) To lower in dignity or estimation; bring into contempt.
2) To lower in character or quality; debase.
3) Chemistry: Of a compound, especially an organic hydrocarbon, to break down (Dictionary.com).

→ de-; → grade.

1) Subdivision of an interval in a scale of measurement.
2) Geometry: Measure of angle, the 360th part of a circle.
3) Math.: Rank of an equation or expression as determined by the sum of the exponents of the variables.

From O.Fr. degré, from V.L. *degradus "a step," from L.L. degredare, from L. → de- "down" + gradus "step."

Darajé, from Ar. darajat "step, ladder."

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.