An Etymological Dictionary of Astronomy and Astrophysics

1. Something brought about by a → cause or agent; a result.
   

2. A scientific law, hypothesis, or phenomenon, such as the → Compton effect, → Coriolis effect, → Doppler effect, → diamond ring effect, → photoelectric effect, and so on.

Etymology (EN): From O.Fr. effect, from L. effectus “accomplishment, performance,” from stem of efficere “to work out, accomplish,” from → ex- “out” + facere “to do, to make,” from PIE base *dhe- “to put, to do;” cf. Mod.Pers. dâdan “to give,”
Mid.Pers. dâdan “to give,” O.Pers./Av. dā- “to give, grant, yield,” dadāiti “he gives;” Skt. dadáti “he gives,” Gk. didomi “I give,” tithenai “to put, set, place;” L. dare “to give, offer;” Rus. delat “to do;” O.H.G. tuon, Ger. tun, O.E. don “to do.”

Etymology (PE): Oskar, from os-, → ex-, + kar-, kardan “to do, make;” Mid.Pers. kardan; O.Pers./Av. kar- “to do, make, build,” Av. kərənaoiti “he makes;” cf. Skt. kr- “to do, to make,” krnoti “he makes, he does,” karoti “he makes, he does,” karma “act, deed;” PIE base k^wer- “to do, to make.”

Actually in operation or in force; concrete; real.

Etymology (EN): M.E., from L. effectivus “practical,” from effect(us), p.p. of efficere, → effect + -ivus “-ive.”

Etymology (PE): Oskarmand, from oskar, → effect + -mand possession suffix.

Of an antenna, the ratio of the extracted power by the antenna to the power per unit area (power density) in the incident wave.

See also: → effective; → aperture.

The effective value of the → Eddington parameter in a non-homogeneous system (porous opacity).

See also: → effective; → Eddington limit; → parameter.

The focal length of an imaging system, which consists of several lenses or mirrors.

See also: → effective; → focal length.

In a → rotating star, the sum of the → gravity and the → centrifugal acceleration. The effective gravity is a function of the rotation velocity (Ω) and the → colatitude (θ). At the pole (θ = 0°) and the equator (θ = 90°) the effective gravity is radial. See also → total gravity.

See also: → effective; → gravity.

Of a galaxy, the distance from its center within which half of the total luminosity is included.

See also: → effective; → radius.

A measure of the surface temperature of a star derived from the total emitted energy,
assuming that the star is a → blackbody emitter (→ Stefan-Boltzmann law, → Planck’s radiation law). See also
→ brightness temperature; → color temperature.

See also: → effective; → temperature.

The degree to which goals are achieved and the extent to which posed problems are solved. Compare → efficiency.

See also: → effective; → -ness.

Power or capacity to produce a desired effect; → effectiveness.

Etymology (EN): From L. efficacia “efficacy, efficiency,” from efficax “powerful, effectual, efficient,” from stem of efficere “accomplish,” → effect.

Etymology (PE): Oskarmandi, → effectiveness.

1. The state or quality of being efficient; competence. Compare → effectiveness.
   

Of a machine, engine, or device, the ratio of the physical quantity which may be stored, transferred, or transformed to the total input quantity.

Etymology (EN): L efficientia, from efficient-, → effect,

• -ia “-y,” an E. suffix of adjectives.

Etymology (PE): Kârâyi, from kârâ “efficient,” from kâr, → work + â present stem of âmadan “to come,” from Av. ay- “to go, to come,” aēiti “goes,” O.Pers. aitiy “goes,” Skt. e- “to come near,” eti “arrival,” Gk. eimi “I go,” L. eo “I go,” Tokharian AB i-; PIE *ei- “to go, to walk.”

Outward flow of a → liquid. Something that → flows out.

Etymology (EN): L. effluxus, p.p. of effluere “to flow out,” from → ex- “out” + fluere “to flow,” → flux.

Etymology (PE): Zošâr, from zo- “out of, from,” → ex-, + šâr, → flux.