An Etymological Dictionary of Astronomy and Astrophysics

To flow out, issue, or proceed, as from a source or origin; come forth; originate; arise (Dictionary.com).

Etymology (EN): From L. emanatus, p.p. of emanare “flow out,” figuratively “arise from, proceed from.”

Etymology (PE): Runemudan “to appear, come out,” literally “to show face,” from ru “face,” → surface, + nemudan “to show,” → display.

An act or instance of emanating; something that emanates or is emanated.

See also: → emanate; → -tion.

A newborn star which is tightly enveloped by a surrounding cloud of gas and dust.

Etymology (EN): Ebedded p.p. of embed, from en- + bed from O.E. bed “bed,” from P.Gmc. *badjam “sleeping place dug in the ground” (O.H.G. betti; Ger. bett); PIE base *bhedh- “to dig, pierce;” cf. Gk. bothyros “pit;” L. fodere “to dig,” fossa “ditch;” → star.

Etymology (PE): Setâré, → star; forupušidé, p.p. of forupušidan, from
foru- “below; beneath; down, downwards;” Mid.Pers. frôt “down, downwards;” O.Pers. fravata “forward, downward;” Skt. pravát- “a sloping path, the slope of a mountain” + pušidan “to cover, conceal, clothe; to wear clothes;” Mid.Pers. pôšidan, pôš- “to cover, put on, wear;” cf. Mid.Pers. pôst; Mod.Pers. pust “skin, hide;” O.Pers. pavastā- “thin clay envelope used to protect unbaked clay tablets;” Skt. pavásta- “cover;” Proto-Indo-Iranian *pauastā- “cloth.”

The act of embodying; the state or fact of being embodied.

Etymology (EN): verbal noun of → embody.

1. To give a concrete form or body to an idea or quality.
   

2. To cause to become a body or part of a body.

Etymology (EN): From en- “in” + → body

Etymology (PE): Tanigândan, from Mid.Pers. tanig “bodily, corporal,” from tan “body,” → if and only if, + -ig, → -ik,

• -ândan suffix of transitive verbs.

1. In several → lunisolar calendars, an → intercalary month employed to preserve a seasonal relationship between the Lunar and Solar cycles. For example, in the → Hebrew calendar the extra month,
   called Adar Alef, was inserted after Shvat
   so that the month of Nissan (month of spring) does not begin in winter.
   

2. In ancient Iranian → solar calendar the additional whole month of 30 days employed every 120 years to compensate for the left-over quarters of days in a calendar year of 365 days (120 years × 0.25 days = 30 days).

Etymology (EN): M.E. embolisme, from M.L. embolismus “intercalation,” from Gk. emballein “to throw into, to insert,” from em- “in”

• ballein “to throw” (source of the medical term embolism “the obstruction (of an artery, etc.) by a clot of blood, bubble of air, etc.”); → month.

Etymology (PE): Behizak, from Mid.Pers. vihezagig or vihezakik
“movable,” from vihezag “movement, progression,” from vihez- “to move, progress;” mâh, → month.

In ancient calendars, a year that contains an → embolismic month.

See also: → embolismic month; → year.

1. Move out of or away from something and become visible.
   

   2. To rise or come forth from or as if from water or other liquid (Dictionary.com).

See also: → ex-, + merge, → submerge.

1. The process of becoming visible after being concealed.
   

   2. The escape of an insect or other invertebrate from an egg, cocoon, or pupal case.
      

   3. The process of coming into existence or prominence (OxfordDictionaries.com).

See also: → emerge; → -ence.

1. Coming into being or notice.
   

   2. Philo.: (of a property) arising as an effect of complex causes and not analyzable simply as the sum of their effects.
      

   3. Ecology: Of or denoting a plant which is taller than the surrounding vegetation, especially a tall tree in a forest (OxfordDictionaries.com).

See also: → emerge; → -ent.

Optics: The → light ray leaving a → medium, in contrast to the → incident ray. If the medium has parallel sides, → angle of incidence and → angle of emergence</i are equal as emergent ray and incident ray are parallel to each other.

Astro.: Same as → egress.

See also: → emerge.

A person who emigrates, as from his or her native country or region (Dictionary.com).

See also: → emigrate + -ant a suffix forming adjectives and nouns from verbs.

To leave one country or region to settle in another; migrate.

See also: → ex-; → migrate.

An act or instance of emigrating; a body of emigrants; emigrants collectively.

See also: Verbal noun of → emigrate.

In an atom, a characteristic amount of energy radiated (as line emission) when an electron moves from an outer orbit to an inner orbit around the nucleus, corresponding to the lost energy of the electron.

Etymology (EN): From L. emissionem “a sending out,” from emiss-, stem of emittere “send forth,” from → ex- “out” + mittere “to send.”

Etymology (PE): Gosil, variant gosi “sending away, dismission;” Mid.Pers. wisé “to despatch” (Parthian Mid.Pers. wsys- “to despatch;” Buddhist Mid.Pers. wsydy “to despatch;” Sogdian ‘ns’yd- “to exhort”), from Proto-Iranian *vi-sid- “to despatch, send off,” from prefix vi- “apart, away, out,” + *sid- “to call.”

In a spectrum, a combination of several closely spaced, often unresolved, → emission lines occurring across a limited range of wavelengths.

See also: → emission; → band.

Electromagnetic flux emitted by a source per unit volume per unit time.

See also: → emission; → coefficient.

Any emission mark in the spectrum of a celestial object resulting from line formation or of unknown origin.

See also: → emission; → feature.

A bright line in the electromagnetic spectrum of a radiating substance caused by emission at a particular wavelength.

See also: → emission; → line.

The product of the square of the electron density times the linear size of the emitting region (in parsecs).

See also: → emission; → measure.

An ionized nebula whose spectrum consists of → emission lines. → planetary nebula; → H II region.

See also: → emission; → nebula.

A spectrum consisting of emission lines, produced when the light does not undergo absorption between the source and the spectrograph.

See also: → emission; → spectrum.

1. Able to emit (radiation, light, or heat).
   
2. Pertaining to → emission.

See also: Verbal adj. from → emit.

The energy emitted from unit surface area of body per second.

See also: → emissive; → power.

The ratio of energy radiated by a material to energy radiated by a black body at the same temperature.

See also: → emissive + → -ity.

To send forth (liquid, light, heat, sound, particles, etc.).

Etymology (EN): Verb of → emission.

Etymology (PE): Gosilidan, infinitive of gosil, → emission.

Any device used to emit light, sound, electrons, or the like.

See also: Agent noun of → emit.

A monarch who rules or reigns over an empire.

Etymology (EN): M.E., from O.Fr. empereor “emperor, leader, ruler,” from L. imperiatorem (nominative imperiator) “commander, emperor,” from p.p. stem of → imperare “to command.”

Etymology (PE): Parmâtyâr, from parmât, present stem of parmâtidan, → imperare, + suffix -yâr, as in šahryâr “sovereign, king,” hušyâr “sober, cautious, intelligent,” kušyâr “name of a physician; industrious” kâmyâr “happy, powerful,” and baxtyâr “fortunate, rich.”

Special stress laid upon, or importance attached to (Dictionary.com).

Etymology (EN): From L. emphasis, from Gk. emphasis “significance, implied meaning,” from emphainein “to show, indicate,” from en “in”

• phainein “to show.” It developed a sense of “extra stress” laid on a word or words to make the significance clear, or to show their importance.

Etymology (PE): Barâvaž, present stem of barâvažidan,
literally “to speak loudly,” from bar- “on, upon, up,” → over-, + âvaž variant of âvâz “voice, sound, noise, clamour,” cf.
Sariqoli awuj “voice, sound,” Wakhi awôγ “voice, sound,” related to vâž, → word.

To give → emphasis to; lay stress upon; stress (Dictionary.com).

See also: → emphasis + → -ize.

1. Uttered, or to be uttered, with emphasis; strongly expressive.
   

2. Using emphasis in speech or action (Dictionary.com).

Etymology (EN): From Gk. emphatikos, variant of emphantikos, from emphainein, → emphasis.

Etymology (PE): Barâvaži, from barâvaž + -i adj. suffix.

1. A political unit having an extensive territory or comprising a number of territories or nations and ruled by a single supreme authority.
   

   2. The territory included in such a unit (TheFreeDictionary).

Etymology (EN): M.E., from O.Fr. empire “rule, authority, kingdom,” from L. imperium “command, dominion, sovereignty,” from → imperare “to command.”

Etymology (PE): Parmâtgân, from parmât, present stem of parmâtidan, → imperare, + -gân suffix denoting relation and place appearinfg in the name of lands and localities (Šâpurgân, Gorgân, Golpâyegân, etc.).

Based on the results of → experiment and → observation only, without → theory.

Etymology (EN): From L. empiricus, from Gk. empeirikos “experienced,” from empeiria “experience,” from empeiros “skilled,” from en- “in” + peira “experiment.”

Etymology (PE): Ârvini, adj. of ârvin “experience, experiment, test,” from prefixed Av. vaēn- (Mod.Pers. bin, present stem of didan “to see, look”) “to see,” aibī-vaēn- “to look, notice;” cf. Parthian Mid.Pers. frwyn- “to foresee,” frwyng “foreseeing,” frwyngyft “foresight,” from Proto-Iranian *fra-uain.

1. In physics, a mathematical equation that predicts observed results, but has no known theoretical basis to explain why it works.
   
2. In chemistry, a simple expression of the relative number of each type of atom in a chemical compound.

See also: → empirical; → formula

A branch of knowledge, including → natural sciences and → social sciences, that is based on observable phenomena and must be capable of being verified by observation.

See also: → empirical; → science.

1. Philo.: The doctrine that all → knowledge of matters of fact derives from experience and that the mind is not furnished with a set of concepts in advance of experience.
   

2. The use of empirical methods (Dictionary.com).

See also: From empiric, → empirical, + → -ism.

Containing nothing; having none of the usual or appropriate contents (Dictionary.com).

Etymology (EN): M.E., from O.E. æmettig “vacant, not occupied,” from æmetta “a leisure,” from æ “not” + -metta, from motan “to have.”

Etymology (PE): Tohi “empty,” → void.

In → graph theory, a graph with any number of → vertices which do not have → edges.

See also: → empty; → graph.

A set containing no → elements.

See also: → empty; → set.

A → cosmological model based on → Einstein’s field equations in which the → Universe is devoid of → matter and → radiation. There are two types of empty Universes: the → de Sitter Universe and the → Milne Universe.

See also: → empty; → Universe.