An Etymological Dictionary of Astronomy and Astrophysics

A → white dwarf whose spectrum shows strong lines of singly ionized helium He II; He I or H may be present. As a DO star cools, the He II will recombine with free electrons to form He I, eventually changing the DO type into a DB white dwarf.

See also: D short for → dwarf; O a convention; → white.

A → white dwarf whose spectrum shows strong lines of singly ionized helium He II; He I or H may be present. As a DO star cools, the He II will recombine with free electrons to form He I, eventually changing the DO type into a DB white dwarf.

See also: D short for → dwarf; O a convention; → white.

1. A written or printed paper furnishing information or evidence, as a passport, deed, bill of sale, or bill of lading; a legal or official paper.
   

2. To furnish with documents. To furnish with references, citations, etc., in support of statements made (Dictionary.com).

Etymology (EN): M.E., from O.Fr. document “written evidence,” from L. documentum “example, proof, lesson,” in M.L. “official written instrument,” from docere “to show, teach,” cognate with Av. daē- “to show,” Pers. andišidan, → think.

Etymology (PE): Dapé, from Mid.Pers. dib, dip “document;” O.Pers. dipī- “inscription;” related to dabir, → secretary; dapidan, infinitive from dap, dapé.

1. A written or printed paper furnishing information or evidence, as a passport, deed, bill of sale, or bill of lading; a legal or official paper.
   

2. To furnish with documents. To furnish with references, citations, etc., in support of statements made (Dictionary.com).

Etymology (EN): M.E., from O.Fr. document “written evidence,” from L. documentum “example, proof, lesson,” in M.L. “official written instrument,” from docere “to show, teach,” cognate with Av. daē- “to show,” Pers. andišidan, → think.

Etymology (PE): Dapé, from Mid.Pers. dib, dip “document;” O.Pers. dipī- “inscription;” related to dabir, → secretary; dapidan, infinitive from dap, dapé.

1. Pertaining to, consisting of, or derived from documents.
   

2. Movies, Television: Based on or re-creating an actual event, era, life story, etc., that purports to be factually accurate and contains no fictional elements (Dictionary.com).

See also: → document; → -ary.

1. Pertaining to, consisting of, or derived from documents.
   

2. Movies, Television: Based on or re-creating an actual event, era, life story, etc., that purports to be factually accurate and contains no fictional elements (Dictionary.com).

See also: → document; → -ary.

1. The use of documentary evidence.
   

2. A furnishing with documents, as to substantiate a claim or the data in a book or article.
   

3. Computers: Manuals, listings, diagrams, and other hard- or soft-copy written and graphic materials that describe the use, operation, maintenance, or design of software or hardware (Dictionary.com).

See also: → document; → -tion.

1. The use of documentary evidence.
   

2. A furnishing with documents, as to substantiate a claim or the data in a book or article.
   

3. Computers: Manuals, listings, diagrams, and other hard- or soft-copy written and graphic materials that describe the use, operation, maintenance, or design of software or hardware (Dictionary.com).

See also: → document; → -tion.

A segment of the → zodiac extending 2.5 degrees, as considered in Babylonian and Hellenistic astrology; plural: dodekatemoria. Dodekatemoria result from a subdivision of each → zodiacal sign into twelve equal parts, each given the name of a → sign, beginning with the name of the sign being divided and continuing throughout the other eleven sequentially. Each zodiacal sign therefore contained a micro-zodiac within its own 30° span. Textual evidence for the micro-zodiac does not antedate the sixth century BC (F. Rochberg, 2010, In the Path of the Moon, BRILL).

Etymology (EN): From Gk. dodekatemorion “twelfth part,” from dodekate “twelfth” (from dodeka “twelve”) + morion “part.”

Etymology (PE): Davâzdahân, from Mid.Pers. dwâzdahân “the twelve ones,” from dwâzdah (Mod.Pers. davâzdah) “twelve;” Av. dvadasa, from dva “→ two”

• dasa “→ ten.”

A segment of the → zodiac extending 2.5 degrees, as considered in Babylonian and Hellenistic astrology; plural: dodekatemoria. Dodekatemoria result from a subdivision of each → zodiacal sign into twelve equal parts, each given the name of a → sign, beginning with the name of the sign being divided and continuing throughout the other eleven sequentially. Each zodiacal sign therefore contained a micro-zodiac within its own 30° span. Textual evidence for the micro-zodiac does not antedate the sixth century BC (F. Rochberg, 2010, In the Path of the Moon, BRILL).

Etymology (EN): From Gk. dodekatemorion “twelfth part,” from dodekate “twelfth” (from dodeka “twelve”) + morion “part.”

Etymology (PE): Davâzdahân, from Mid.Pers. dwâzdahân “the twelve ones,” from dwâzdah (Mod.Pers. davâzdah) “twelve;” Av. dvadasa, from dva “→ two”

• dasa “→ ten.”

A domestic mammal related to the wolf and bred in many varieties.

Etymology (EN): From M.E. dogge, from O.E. docga “hound, powerful breed of dog,” cognate with Scots dug</i< “dog,” Dan. dogge, Ger. Dogge, of unknown origin.

Etymology (PE): Sag “dog” (Lori say, sayu “puppy;” Pashto spay, spie “bitch;” Semnâni esba; Sangesari əsba; Kajali of Khlkhâl esbé; Tâleshi of Vizna səba; Abyâni kuyâ);
from Mid.Pers. sag “dog;” O.Pers. *saka-; Median *spaka-; Av. spā-; cf. Skt. svâ-; L.
canis “dog;” Gk. kuon; O.E. hund, E. hound, Ger. Hund; PIE *kwon-.

A domestic mammal related to the wolf and bred in many varieties.

Etymology (EN): From M.E. dogge, from O.E. docga “hound, powerful breed of dog,” cognate with Scots dug</i< “dog,” Dan. dogge, Ger. Dogge, of unknown origin.

Etymology (PE): Sag “dog” (Lori say, sayu “puppy;” Pashto spay, spie “bitch;” Semnâni esba; Sangesari əsba; Kajali of Khlkhâl esbé; Tâleshi of Vizna səba; Abyâni kuyâ);
from Mid.Pers. sag “dog;” O.Pers. *saka-; Median *spaka-; Av. spā-; cf. Skt. svâ-; L.
canis “dog;” Gk. kuon; O.E. hund, E. hound, Ger. Hund; PIE *kwon-.

1. A specific tenet or doctrine authoritatively laid down, as by a church.
   

2. An official system of principles or tenets concerning faith, morals, behavior, etc., as of a church.
   

3. Prescribed doctrine proclaimed as unquestionably true by a particular group (Dictionary.com).

Etymology (EN): L. dogma “philosophical tenet,” from Gk. dogma “opinion, tenet,” literally “that which one thinks is true,” from dokein “to seem good, think,” cognate with Pers. andišé “thought,” dis, → form.

Etymology (PE): Kiš “dogma, religion,” from Mid.Pers. kêš “religion, faith, dogma;” Av. tkaēša- “teaching,” kaeš-, kaš- “to teach;” PIE *k^weis- “to observe, see” (Cheung 2007).

1. A specific tenet or doctrine authoritatively laid down, as by a church.
   

2. An official system of principles or tenets concerning faith, morals, behavior, etc., as of a church.
   

3. Prescribed doctrine proclaimed as unquestionably true by a particular group (Dictionary.com).

Etymology (EN): L. dogma “philosophical tenet,” from Gk. dogma “opinion, tenet,” literally “that which one thinks is true,” from dokein “to seem good, think,” cognate with Pers. andišé “thought,” dis, → form.

Etymology (PE): Kiš “dogma, religion,” from Mid.Pers. kêš “religion, faith, dogma;” Av. tkaēša- “teaching,” kaeš-, kaš- “to teach;” PIE *k^weis- “to observe, see” (Cheung 2007).

1. Of, pertaining to, or of the nature of a dogma or dogmas; doctrinal.
   

2. Asserting opinions in a doctrinaire or arrogant manner; opinionated (Dictionary.com).

See also: → dogma + -t- + → -ic.

1. Of, pertaining to, or of the nature of a dogma or dogmas; doctrinal.
   

2. Asserting opinions in a doctrinaire or arrogant manner; opinionated (Dictionary.com).

See also: → dogma + -t- + → -ic.

The tendency to lay down principles as undeniably true, without consideration of evidence or the opinions of others (OxfordDictionaries.com).

See also: → dogmatic;→ -ism.

The tendency to lay down principles as undeniably true, without consideration of evidence or the opinions of others (OxfordDictionaries.com).

See also: → dogmatic;→ -ism.

1. Math.: The set of x values that can go into a function f(x). Compare with → codomain and → range.
   

2. Ferromagnetism: → magnetic domain.

Etymology (EN): From M.Fr. domaine “domain, estate,” from O.Fr. demaine “lord’s estate,” from L. dominium “property, dominion,” from dominus “master of a household,” from domus “house;” cognate with Pers. dam, as below; Gk. domos “house;” O.C.S. domu , Russ. dom “house;” Lith. dimstis “enclosed court, property;” O.E. timber “building, structure”); PIE base *dem-/*dom- “to build.”

Etymology (PE): Daman, from Av. dəmāna- “house,” dami “in the house;” cf. Sogd. δmān “house;” Mod.Pers. dam “wealth, means of comfort” (often as dam o dastgâh); “threshold, doorway;” Gilaki dâmana “ceiling;” Sariqoli waδem, Yazghulami wəδem “ceiling;” Skt. dám- “house;” Proto-Iranian *damH- “to build;” Gk. demo “I build;” L. domus “house,” as above.

1. Math.: The set of x values that can go into a function f(x). Compare with → codomain and → range.
   

2. Ferromagnetism: → magnetic domain.

Etymology (EN): From M.Fr. domaine “domain, estate,” from O.Fr. demaine “lord’s estate,” from L. dominium “property, dominion,” from dominus “master of a household,” from domus “house;” cognate with Pers. dam, as below; Gk. domos “house;” O.C.S. domu , Russ. dom “house;” Lith. dimstis “enclosed court, property;” O.E. timber “building, structure”); PIE base *dem-/*dom- “to build.”

Etymology (PE): Daman, from Av. dəmāna- “house,” dami “in the house;” cf. Sogd. δmān “house;” Mod.Pers. dam “wealth, means of comfort” (often as dam o dastgâh); “threshold, doorway;” Gilaki dâmana “ceiling;” Sariqoli waδem, Yazghulami wəδem “ceiling;” Skt. dám- “house;” Proto-Iranian *damH- “to build;” Gk. demo “I build;” L. domus “house,” as above.

In a → ferroelectric substance, the transition layer between two → domains magnetized in different directions. It is of finite thickness ans has nonuniform → magnetization.

See also: → domain; → wall.

In a → ferroelectric substance, the transition layer between two → domains magnetized in different directions. It is of finite thickness ans has nonuniform → magnetization.

See also: → domain; → wall.

A vault, having a circular plan and usually in the form of a portion of a sphere, that shelters an optical telescope.
Geology: Rounded volcanic structure produced by eruption or intrusion of viscous high-silica magma.

An uplift that is round or elliptical in map view with beds dipping away in all directions from a central point.

Etymology (EN): From Fr. dôme, from Gk. doma “house, housetop,” related to domos “house”
(PIE *domo-/*domu- “house, household;” cf. Av. dam-, dəmāna- “house,” Skt. dám- “house,” Gk. doma “house,”
L. domus “house,” Rus. dom “house,” Lith. dimstis “enclosed court, property,” O.E. timber “building, structure”).

Etymology (PE): Mid.Pers. gumbat, gônbat.

A vault, having a circular plan and usually in the form of a portion of a sphere, that shelters an optical telescope.
Geology: Rounded volcanic structure produced by eruption or intrusion of viscous high-silica magma.

An uplift that is round or elliptical in map view with beds dipping away in all directions from a central point.

Etymology (EN): From Fr. dôme, from Gk. doma “house, housetop,” related to domos “house”
(PIE *domo-/*domu- “house, household;” cf. Av. dam-, dəmāna- “house,” Skt. dám- “house,” Gk. doma “house,”
L. domus “house,” Rus. dom “house,” Lith. dimstis “enclosed court, property,” O.E. timber “building, structure”).

Etymology (PE): Mid.Pers. gumbat, gônbat.

One of small covers that can be moved along the dome slit to vary the slit size.

See also: → dome; → hatch.

One of small covers that can be moved along the dome slit to vary the slit size.

See also: → dome; → hatch.

A pair of rolling lids that are used to open or close the dome slit.

Etymology (EN): → dome; shutter from to shut, from O.E. scyttan from W.Gmc. *skutjanan + → -er.

Etymology (PE): Bastâr, from bast, past tense stem of bastan

• -âr. Bastan, from Mid.Pers. bastan/vastan “to bind, shut,” Av./O.Pers. band- “to bind, fetter,” banda- “band, tie,” Skt. bandh- “to bind, tie, fasten,” PIE *bhendh- “to bind,” cf. Ger. binden, E. bind, → band. The suffix -âr creates creates agent nouns; → dome.

A pair of rolling lids that are used to open or close the dome slit.

Etymology (EN): → dome; shutter from to shut, from O.E. scyttan from W.Gmc. *skutjanan + → -er.

Etymology (PE): Bastâr, from bast, past tense stem of bastan

• -âr. Bastan, from Mid.Pers. bastan/vastan “to bind, shut,” Av./O.Pers. band- “to bind, fetter,” banda- “band, tie,” Skt. bandh- “to bind, tie, fasten,” PIE *bhendh- “to bind,” cf. Ger. binden, E. bind, → band. The suffix -âr creates creates agent nouns; → dome.

An opening along the spherical body of a dome through which an optical telescope can observe.

See also: → dome; → slit.

An opening along the spherical body of a dome through which an optical telescope can observe.

See also: → dome; → slit.

Of a → non-zero polynomial, the coefficient of the → monomial which has the highest → degree.

See also: Dominant, adj. from → dominant; → coefficient.

Of a → non-zero polynomial, the coefficient of the → monomial which has the highest → degree.

See also: Dominant, adj. from → dominant; → coefficient.

To have control, authority, or influence; to be the most important or conspicuous person or thing.
→ core-dominated quasar, → dominant coefficient, → dominated series, → domination, → lobe-dominated quasar, → matter-dominated Universe, → radiation-dominated Universe.

Etymology (EN): From L. dominatus, p.p. of dominari “to rule, dominate, govern,” from dominus, → domain.

Etymology (PE): Ciridan, from ciré “dominant; powerful; victorious,” Mid.Pers. cêr “victorious, brave,” Av. cirya- “able, brave.”

To have control, authority, or influence; to be the most important or conspicuous person or thing.
→ core-dominated quasar, → dominant coefficient, → dominated series, → domination, → lobe-dominated quasar, → matter-dominated Universe, → radiation-dominated Universe.

Etymology (EN): From L. dominatus, p.p. of dominari “to rule, dominate, govern,” from dominus, → domain.

Etymology (PE): Ciridan, from ciré “dominant; powerful; victorious,” Mid.Pers. cêr “victorious, brave,” Av. cirya- “able, brave.”

A → series if each of its → terms does not exceed, in absolute value, the corresponding term of some convergent numerical series with positive terms.

See also: Dominated, p.p. of → dominate; → series.

A → series if each of its → terms does not exceed, in absolute value, the corresponding term of some convergent numerical series with positive terms.

See also: Dominated, p.p. of → dominate; → series.

An act or instance of dominating.

See also: Verbal noun of → dominate.

An act or instance of dominating.

See also: Verbal noun of → dominate.

In a semiconductor, an impurity which may induce electric conduction by providing free electrons. → acceptor; → impurity.

Etymology (EN): M.E. donour, from O.Fr. doneur, from L. donator, from donare “to give as a gift,” donum “gift,” dare “to give,” cognate with Pers. dâdan “to give,” from PIE base *do- “to give.”

Etymology (PE): Dahandé “giver,” from dâdan “to give,” Mid.Pers. dâdan “to give,” O.Pers./Av. dā- “to give, grant, yield,” Av. dadāiti “he gives,” Skt. dadâti “he gives,” Gk. didomi “I give,” PIE base *do- “to give.” For L. cognates see above.

In a semiconductor, an impurity which may induce electric conduction by providing free electrons. → acceptor; → impurity.

Etymology (EN): M.E. donour, from O.Fr. doneur, from L. donator, from donare “to give as a gift,” donum “gift,” dare “to give,” cognate with Pers. dâdan “to give,” from PIE base *do- “to give.”

Etymology (PE): Dahandé “giver,” from dâdan “to give,” Mid.Pers. dâdan “to give,” O.Pers./Av. dā- “to give, grant, yield,” Av. dadāiti “he gives,” Skt. dadâti “he gives,” Gk. didomi “I give,” PIE base *do- “to give.” For L. cognates see above.

In a → binary system, a star whose gas is
→ accreted by a compact companion. The donor may be a → giant or a → supergiant with an enormously distended atmosphere and a significant → stellar wind, or a star filling its → Roche lobe in a → close binary.

See also: → donor; → star.

In a → binary system, a star whose gas is
→ accreted by a compact companion. The donor may be a → giant or a → supergiant with an enormously distended atmosphere and a significant → stellar wind, or a star filling its → Roche lobe in a → close binary.

See also: → donor; → star.

A movable barrier by which an entry is closed and opened.

Etymology (EN): M.E. dore, O.E. duru “door, dor gate;” akin to Ger. Tür, O.Norse dyrr, O.Irish dorus, Pers. dar, as below.

Etymology (PE): Dar “door,” Mid.Pers. dar; O.Pers. duvara-; Av. dvar-;
cf. Skt. dvár-; Gk. thura; L. fores;
Lith. dvaras “court-yard;” E. door, as above; PIE *dhwer-/*dhwor- “door, gate.”

A movable barrier by which an entry is closed and opened.

Etymology (EN): M.E. dore, O.E. duru “door, dor gate;” akin to Ger. Tür, O.Norse dyrr, O.Irish dorus, Pers. dar, as below.

Etymology (PE): Dar “door,” Mid.Pers. dar; O.Pers. duvara-; Av. dvar-;
cf. Skt. dvár-; Gk. thura; L. fores;
Lith. dvaras “court-yard;” E. door, as above; PIE *dhwer-/*dhwor- “door, gate.”

Electronics: To add or treat a pure semiconductor with an impurity (dopant) to change its electrical properties.

Etymology (EN): From Du. doop “thick dipping sauce,” from dopen “to dip.”

Etymology (PE): Âqârdan “to mix, to soak,” cf. Sogdian wγyr- “to soak, steep,” zγr “moisture,” Ossetic qaryn “to permeate, seep through (of liquid),” Skt. ghar-, jigharti “to sprinkle, drip.”

Electronics: To add or treat a pure semiconductor with an impurity (dopant) to change its electrical properties.

Etymology (EN): From Du. doop “thick dipping sauce,” from dopen “to dip.”

Etymology (PE): Âqârdan “to mix, to soak,” cf. Sogdian wγyr- “to soak, steep,” zγr “moisture,” Ossetic qaryn “to permeate, seep through (of liquid),” Skt. ghar-, jigharti “to sprinkle, drip.”

The addition of minute quantities of impurities to a semiconductor to achieve a desired characteristic.

See also: Verbal noun of → dope.

The addition of minute quantities of impurities to a semiconductor to achieve a desired characteristic.

See also: Verbal noun of → dope.

In atomic physics, the broadening of an emission or absorption line due to the Doppler effect. Random motions of molecules or atoms of the gas that is emitting or absorbing the radiant energy shift the apparent wavelength of each emitter, and the cumulative effect of indivisual shifts is to broaden the line.

See also: → Doppler effect; → broadening.

In atomic physics, the broadening of an emission or absorption line due to the Doppler effect. Random motions of molecules or atoms of the gas that is emitting or absorbing the radiant energy shift the apparent wavelength of each emitter, and the cumulative effect of indivisual shifts is to broaden the line.

See also: → Doppler effect; → broadening.

Change in frequency of a wave (light, sound) due to the relative motion of source and receiver. Approaching objects have their wavelengths shortened. Receding objects have emitted wavelengths lengthened.

See also: Doppler, after Christian Andreas Doppler (1803-1853), Austrian physicist who first described how the observed frequency of sound and light waves is affected by the relative motion of the source and the detector; → effect.

Change in frequency of a wave (light, sound) due to the relative motion of source and receiver. Approaching objects have their wavelengths shortened. Receding objects have emitted wavelengths lengthened.

See also: Doppler, after Christian Andreas Doppler (1803-1853), Austrian physicist who first described how the observed frequency of sound and light waves is affected by the relative motion of the source and the detector; → effect.

The shape of the spectral line resulting from the Doppler broadening.

See also: → Doppler effect; → profile.

The shape of the spectral line resulting from the Doppler broadening.

See also: → Doppler effect; → profile.

Effect of the relative motion of a wave source (light, sound) and the observer. If the source is moving away, the wavelength is stretched (shifted toward lower frequencies). If the source is approaching, the wavelength is compressed (shifted toward higher frequencies). These effects, known as Doppler shifts, are in the case of light waves called redshift and blueshift, respectively.

See also: → Doppler effect; → shift.

Effect of the relative motion of a wave source (light, sound) and the observer. If the source is moving away, the wavelength is stretched (shifted toward lower frequencies). If the source is approaching, the wavelength is compressed (shifted toward higher frequencies). These effects, known as Doppler shifts, are in the case of light waves called redshift and blueshift, respectively.

See also: → Doppler effect; → shift.

A technique using a series of Doppler-shifted line profiles at different orbital phases in cataclysmic variable stars (CVs) to image the compact system in the light of a particular emission line. Although developed for CVs, the method has wider applications. An alternative method is → eclipse mapping.

See also: → Doppler effect; → tomography.

A technique using a series of Doppler-shifted line profiles at different orbital phases in cataclysmic variable stars (CVs) to image the compact system in the light of a particular emission line. Although developed for CVs, the method has wider applications. An alternative method is → eclipse mapping.

See also: → Doppler effect; → tomography.

The Swordfish. A constellation in the southern hemisphere near → Reticulum and → Pictor. It contains most of the → Large Magellanic Cloud which laps over to some extent into the neighboring constellation → Mensa. The south → ecliptic pole also lies within this constellation. Abbreviation: Dor, Genitive: Doradus.

Etymology (EN): Dorado, from Sp., from L.L. deaurutus, p.p. of deaurare “to gild,” from → de- + aurium “gold.”
Dorado (Coryphaena hippurus) is a surface-dwelling fish found in off-shore tropical and subtropical waters worldwide. It is distinguished by dazzling golden colors on the sides.

Etymology (PE): Mâhi “fish,” from Mid.Pers. mâhik, Av. masya-, cf. Skt. matsya-, Pali maccha-.
Zarrin “golden,” from zarr “gold,” Mid.Pers. zarr, Av. zaranya-, zarənu- “gold,”
O.Pers. daraniya- “gold,” Skt. hiranya- “gold;” also Av. zaray-, zairi- “yellow, green,” Mod.Pers. zard “yellow,” Skt. hari- “yellow, green,” Gk. Khloe lit. “young green shoot,” L. helvus “yellowish, bay,” Rus. zeltyj “yellow,” P.Gmc. *gelwaz, Du. geel, Ger. gelb, E. yellow.

The Swordfish. A constellation in the southern hemisphere near → Reticulum and → Pictor. It contains most of the → Large Magellanic Cloud which laps over to some extent into the neighboring constellation → Mensa. The south → ecliptic pole also lies within this constellation. Abbreviation: Dor, Genitive: Doradus.

Etymology (EN): Dorado, from Sp., from L.L. deaurutus, p.p. of deaurare “to gild,” from → de- + aurium “gold.”
Dorado (Coryphaena hippurus) is a surface-dwelling fish found in off-shore tropical and subtropical waters worldwide. It is distinguished by dazzling golden colors on the sides.

Etymology (PE): Mâhi “fish,” from Mid.Pers. mâhik, Av. masya-, cf. Skt. matsya-, Pali maccha-.
Zarrin “golden,” from zarr “gold,” Mid.Pers. zarr, Av. zaranya-, zarənu- “gold,”
O.Pers. daraniya- “gold,” Skt. hiranya- “gold;” also Av. zaray-, zairi- “yellow, green,” Mod.Pers. zard “yellow,” Skt. hari- “yellow, green,” Gk. Khloe lit. “young green shoot,” L. helvus “yellowish, bay,” Rus. zeltyj “yellow,” P.Gmc. *gelwaz, Du. geel, Ger. gelb, E. yellow.

1. The giving of a dose.
   

   2. Regulation or determination of doses.
      

   3. The addition of an ingredient or the application of an agent in a measured dose (Merriam-Webster.com).

See also: From Fr. dosage, → dose.

1. The giving of a dose.
   

   2. Regulation or determination of doses.
      

   3. The addition of an ingredient or the application of an agent in a measured dose (Merriam-Webster.com).

See also: From Fr. dosage, → dose.

1a) A specified quantity of medicine taken at any one time.

1b) The amount of radiation administered as therapy to a given site.

2a) To give or prescribe something, such as medicine, in specified amounts.

2b) To give someone a dose of medicine to.

Etymology (EN): M.E., from M.Fr. dose, from L.L. dosis, from Gk. dosis “a portion prescribed,” literally “a giving,” used by Galen and other Gk. physicians to mean an amount of medicine, from stem of didonai “to give.”

Etymology (PE): Doz, loan from Fr., as above. Dozidan infinitive from doz.

1a) A specified quantity of medicine taken at any one time.

1b) The amount of radiation administered as therapy to a given site.

2a) To give or prescribe something, such as medicine, in specified amounts.

2b) To give someone a dose of medicine to.

Etymology (EN): M.E., from M.Fr. dose, from L.L. dosis, from Gk. dosis “a portion prescribed,” literally “a giving,” used by Galen and other Gk. physicians to mean an amount of medicine, from stem of didonai “to give.”

Etymology (PE): Doz, loan from Fr., as above. Dozidan infinitive from doz.

1. The administration of a dose.
   

   2. → dosage.

See also: → dose; → -ing.

1. The administration of a dose.
   

   2. → dosage.

See also: → dose; → -ing.

Same as → scalar product.

Etymology (EN): O.E. dott “speck, head of a boil,” perhaps related to Norw. dot “lump, knot,” Du. dot “knot, wisp;” cognate with O.H.G. tutta “nipple;” → product.

Etymology (PE): Bastâk, → product; marpeli, → scalar.

Same as → scalar product.

Etymology (EN): O.E. dott “speck, head of a boil,” perhaps related to Norw. dot “lump, knot,” Du. dot “knot, wisp;” cognate with O.H.G. tutta “nipple;” → product.

Etymology (PE): Bastâk, → product; marpeli, → scalar.

1. Composed of two like parts or members.
   

2. Twice as large, heavy, strong, etc.
   

3. Anything that is twofold in size or amount or twice the usual size, quantity, strength, etc.

Etymology (EN): From O.Fr. duble, from L. duplus “twofold” (Gk. diplos “double”),
from duo “two” + -plus “fold.”

Etymology (PE): Dotâyi, from dotâ, from
do “two,” akin to L. duo, + tâ “fold, plait, ply; piece, part,” Mid.Pers. tâg “piece, part.”

1. Composed of two like parts or members.
   

2. Twice as large, heavy, strong, etc.
   

3. Anything that is twofold in size or amount or twice the usual size, quantity, strength, etc.

Etymology (EN): From O.Fr. duble, from L. duplus “twofold” (Gk. diplos “double”),
from duo “two” + -plus “fold.”

Etymology (PE): Dotâyi, from dotâ, from
do “two,” akin to L. duo, + tâ “fold, plait, ply; piece, part,” Mid.Pers. tâg “piece, part.”

An electron-photon interaction that can be thought of as a → Compton scattering event associated with the production or destruction of an extra photon.

See also: → double; → Compton; → scattering.

An electron-photon interaction that can be thought of as a → Compton scattering event associated with the production or destruction of an extra photon.

See also: → double; → Compton; → scattering.

The simplest case of a → multiple integral.

See also: → double; → integral.

The simplest case of a → multiple integral.

See also: → double; → integral.

A → binary pulsar consisting of two pulsars. The only known example is PSR J0737-3039 (A and B), discovered in 2003 (Burgay et al. Nature 426, 531). The rotation periods of the pulsars are 22.7 and 2.8 milliseconds respectively. Each of them has a mass about 1.3 times that of the Sun and revolves
around their → center of gravity with a period of 2.4 hours. According to the theory of → general relativity, such a binary should lose energy through the emission of → gravitational waves.
As deduced from the change in orbital period, the separation of the pulsars is reducing by about 7 mm per day, in exact agreement with theory. It is expected that the pulsars will eventually merge in about 85 million years.

See also: → double; → pulsar.

A → binary pulsar consisting of two pulsars. The only known example is PSR J0737-3039 (A and B), discovered in 2003 (Burgay et al. Nature 426, 531). The rotation periods of the pulsars are 22.7 and 2.8 milliseconds respectively. Each of them has a mass about 1.3 times that of the Sun and revolves
around their → center of gravity with a period of 2.4 hours. According to the theory of → general relativity, such a binary should lose energy through the emission of → gravitational waves.
As deduced from the change in orbital period, the separation of the pulsars is reducing by about 7 mm per day, in exact agreement with theory. It is expected that the pulsars will eventually merge in about 85 million years.

See also: → double; → pulsar.

Formation of two refracted rays of light from a single incident ray; property of certain crystals, notably calcite.

See also: → double; → refraction.

Formation of two refracted rays of light from a single incident ray; property of certain crystals, notably calcite.

See also: → double; → refraction.

A → root x₀ of function f(x), if f(x₀) = 0, df/dx | x₀ = 0, and d²f/dx² | x₀≠ 0. See also → simple root.

See also: → double; → root.

A → root x₀ of function f(x), if f(x₀) = 0, df/dx | x₀ = 0, and d²f/dx² | x₀≠ 0. See also → simple root.

See also: → double; → root.

A situation in the evolution of an → asymptotic giant branch star whereby both hydrogen and helium shells provide energy alternatively. As the burning → helium shell approaches the hydrogen-helium discontinuity, its luminosity decreases because it runs out of the fuel. As a consequence, the layers above contract in response, thus heating the extinguished → hydrogen shell until it is re-ignited. However, the shells do not burn at the same rate: the He burning shell becomes thermally unstable and undergoes periodic → thermal pulses.

See also: → double; → shell; → burning.

A situation in the evolution of an → asymptotic giant branch star whereby both hydrogen and helium shells provide energy alternatively. As the burning → helium shell approaches the hydrogen-helium discontinuity, its luminosity decreases because it runs out of the fuel. As a consequence, the layers above contract in response, thus heating the extinguished → hydrogen shell until it is re-ignited. However, the shells do not burn at the same rate: the He burning shell becomes thermally unstable and undergoes periodic → thermal pulses.

See also: → double; → shell; → burning.

A pair of adjacent holes or slits made on a dark and plane surface, used in optical experiments, such as interference and diffraction.

See also: → double; → slit.

A pair of adjacent holes or slits made on a dark and plane surface, used in optical experiments, such as interference and diffraction.

See also: → double; → slit.

An apparently single star which better observational resolution shows it to be a pair of closely lying stars. They may or may not be physically related.

See also: → double; → star.

An apparently single star which better observational resolution shows it to be a pair of closely lying stars. They may or may not be physically related.

See also: → double; → star.

Same as → diplopia.

See also: → double; → vision.

Same as → diplopia.

See also: → double; → vision.

A → double-lined binary with two
→ white dwarf components. Short-period double white dwarfs can lose → orbital angular momentum by emitting → gravitational radiation and if the total mass of the binary exceeds the → Chandrasekhar limit, their eventual → merger might produce a → Type Ia supernova.

See also: → double; → white; → dwarf.

A → double-lined binary with two
→ white dwarf components. Short-period double white dwarfs can lose → orbital angular momentum by emitting → gravitational radiation and if the total mass of the binary exceeds the → Chandrasekhar limit, their eventual → merger might produce a → Type Ia supernova.

See also: → double; → white; → dwarf.

A system of evolved → binary stars in which both → components have ejected their envelopes and evolve toward → white dwarf stage. So far a half dozen double-degenerate → binary systems are known, for example Henize 2-248 (M. Santander-Garcia et al., 2015, 518, 5).

See also: → double; → degenerate; → binary; → system.

A system of evolved → binary stars in which both → components have ejected their envelopes and evolve toward → white dwarf stage. So far a half dozen double-degenerate → binary systems are known, for example Henize 2-248 (M. Santander-Garcia et al., 2015, 518, 5).

See also: → double; → degenerate; → binary; → system.

An instability involving two layers of fluid with opposite gradients of properties. Same as → fingering instability. See also → salt finger. Double-diffusive instabilities commonly occur in any astrophysical fluid that is stable according to the → Ledoux criterion, as long as the entropy and chemical stratifications have opposing contributions to the dynamical stability of the system. They drive weak forms of convection, and can cause substantial heat and compositional → mixing. Two cases can be distinguished. In fingering convection,

entropy is stably stratified (∇ - ∇ad < 0), but chemical composition is unstably stratified (∇μ < 0); it is often referred to as → thermohaline convection by analogy with the oceanographic context in which the instability was first discovered. In oscillatory double-diffusive convection, entropy is unstably stratified (∇ - ∇ad > 0), but chemical composition is stably stratified (∇μ > 0); it is related to semiconvection, but can occur even when the → opacity
is independent of composition (P. Garaud, 2014, arXiv:1401.0928).

See also: → double;→ diffusive; → system.

An instability involving two layers of fluid with opposite gradients of properties. Same as → fingering instability. See also → salt finger. Double-diffusive instabilities commonly occur in any astrophysical fluid that is stable according to the → Ledoux criterion, as long as the entropy and chemical stratifications have opposing contributions to the dynamical stability of the system. They drive weak forms of convection, and can cause substantial heat and compositional → mixing. Two cases can be distinguished. In fingering convection,

entropy is stably stratified (∇ - ∇ad < 0), but chemical composition is unstably stratified (∇μ < 0); it is often referred to as → thermohaline convection by analogy with the oceanographic context in which the instability was first discovered. In oscillatory double-diffusive convection, entropy is unstably stratified (∇ - ∇ad > 0), but chemical composition is stably stratified (∇μ > 0); it is related to semiconvection, but can occur even when the → opacity
is independent of composition (P. Garaud, 2014, arXiv:1401.0928).

See also: → double;→ diffusive; → system.

A → spectroscopic binary in which the → spectral lines of both stars are seen and the lines are alternatively double and single. Same as → SB2 binary. See also: → single-lined binary.

See also: → double; → line; → binary

A → spectroscopic binary in which the → spectral lines of both stars are seen and the lines are alternatively double and single. Same as → SB2 binary. See also: → single-lined binary.

See also: → double; → line; → binary

A → double-lined spectroscopic binary
whose → light curve is typical of an → eclipsing binary.

See also: → double; → line; → eclipsing; → binary.

A → double-lined spectroscopic binary
whose → light curve is typical of an → eclipsing binary.

See also: → double; → line; → eclipsing; → binary.

Same as → double-lined binary.

See also: → double; → line; → spectroscopic; → binary.

Same as → double-lined binary.

See also: → double; → line; → spectroscopic; → binary.

A → galaxy that emits radio energy from two regions located on opposite sides of the galaxy.

See also: → double; → lobe; → radio; → source.

A → galaxy that emits radio energy from two regions located on opposite sides of the galaxy.

See also: → double; → lobe; → radio; → source.

An experiment of → diffraction and → interference of two light beams using a → double slit; → Young’s experiment.

See also: → double; → slit; → experiment.

An experiment of → diffraction and → interference of two light beams using a → double slit; → Young’s experiment.

See also: → double; → slit; → experiment.

A pair of forbidden spectral lines of the same atom arising from a common upper excitation level, for example [O III] λ 5007 and [O III] λ 4959, [N II] λ 6584 and [N II] λ 6548, and [S II] λ 6717,
[S II] λ 6731.
A pair of associated lines arising from transitions having a common lower energy level in a spectrum characteristic of the alkali metals.

Etymology (EN): From O.Fr. doublet, from → double + -et diminutive suffix.

Etymology (PE): Dotâyé, from dotâ→ double + -(y)é nuance suffix.

A pair of forbidden spectral lines of the same atom arising from a common upper excitation level, for example [O III] λ 5007 and [O III] λ 4959, [N II] λ 6584 and [N II] λ 6548, and [S II] λ 6717,
[S II] λ 6731.
A pair of associated lines arising from transitions having a common lower energy level in a spectrum characteristic of the alkali metals.

Etymology (EN): From O.Fr. doublet, from → double + -et diminutive suffix.

Etymology (PE): Dotâyé, from dotâ→ double + -(y)é nuance suffix.

1. To a double measure or degree.
   

2. In a double manner. → doubly convex, → doubly ionized, → doubly refracting crystal.

See also: → double; → -ly
(; → twice).

1. To a double measure or degree.
   

2. In a double manner. → doubly convex, → doubly ionized, → doubly refracting crystal.

See also: → double; → -ly
(; → twice).

Describing a → lens which is → convex on both sides.

See also: → doubly; → convex.

Describing a → lens which is → convex on both sides.

See also: → doubly; → convex.

An atom that has lost two of its external electrons, for example O⁺⁺ ([O III]).

See also: → doubly; → ionized.

An atom that has lost two of its external electrons, for example O⁺⁺ ([O III]).

See also: → doubly; → ionized.

A → transparent → crystalline substance (such as calcite, quartz, and tourmaline) that is → anisotropic relative to the → speed of light. A ray incident normally on such crystals is broken up into two rays in traversing the crystal, → ordinary ray and → extraordinary ray.

See also: → doubly; → refracting; → crystal.

A → transparent → crystalline substance (such as calcite, quartz, and tourmaline) that is → anisotropic relative to the → speed of light. A ray incident normally on such crystals is broken up into two rays in traversing the crystal, → ordinary ray and → extraordinary ray.

See also: → doubly; → refracting; → crystal.

1. A feeling of uncertainty about the truth, reality, or nature of something. → skepticism.
   

   2. To be uncertain about; consider questionable or unlikely; hesitate to believe (Dictionary.com).

Etymology (EN): M.E. douten, from O.Fr. douter “doubt, be doubtful,” from L. dubitare “to doubt, question, hesitate” (related to dubius “uncertain”), from duo, “→ two,”

• habere “have, hold,” with a sense of “of having two minds, undecided between two things;” cf. Pers. dodeli, as below.

Etymology (PE): Gomân, from Mid.Pers. gumân “doubt;” ultimately from Proto-Ir. *ui-man-, from suffixed *man- “to think,” → idea.
Šakk, loan from Ar.
Dodeli, literally “having two minds,” from do, → two, + del, → heart (also meaning “soul, spirit, will, desire, courage, mind”); cf. Sogdian δβanā (from *dwa-nā), Ger. Zweifel, and L. dubius, as above.

1. A feeling of uncertainty about the truth, reality, or nature of something. → skepticism.
   

   2. To be uncertain about; consider questionable or unlikely; hesitate to believe (Dictionary.com).

Etymology (EN): M.E. douten, from O.Fr. douter “doubt, be doubtful,” from L. dubitare “to doubt, question, hesitate” (related to dubius “uncertain”), from duo, “→ two,”

• habere “have, hold,” with a sense of “of having two minds, undecided between two things;” cf. Pers. dodeli, as below.

Etymology (PE): Gomân, from Mid.Pers. gumân “doubt;” ultimately from Proto-Ir. *ui-man-, from suffixed *man- “to think,” → idea.
Šakk, loan from Ar.
Dodeli, literally “having two minds,” from do, → two, + del, → heart (also meaning “soul, spirit, will, desire, courage, mind”); cf. Sogdian δβanā (from *dwa-nā), Ger. Zweifel, and L. dubius, as above.

Toward or in a lower physical position.
See also:

→ download, → downgrade, → upload, → downsizing, → meltdown, → overload, → spin-down, → top-down structure formation.

Etymology (EN): M.E. doun, from O.E. dune “downward,” short for adune, ofdune, from a-, of “off, from” + dune “hill.”

Etymology (PE): Pâyin “bottom, below; at the foot of,” from pâ(y) “foot; step;” Mid.Pers. pâd, pây; Av. pad- “foot;” cf. Skt. pat; Gk. pos, genitive podos; L. pes, genitive pedis; E. foot; Ger. Fuss; Fr. pied; PIE *pod-/*ped-.
Foru “down, downward; below, under, beneath; low,” Mid.Pers. frôt “down, downward;” O.Pers. fravata “forward, downward;” Skt. pravát- “a sloping path, the slope of a mountain.”

Toward or in a lower physical position.
See also:

→ download, → downgrade, → upload, → downsizing, → meltdown, → overload, → spin-down, → top-down structure formation.

Etymology (EN): M.E. doun, from O.E. dune “downward,” short for adune, ofdune, from a-, of “off, from” + dune “hill.”

Etymology (PE): Pâyin “bottom, below; at the foot of,” from pâ(y) “foot; step;” Mid.Pers. pâd, pây; Av. pad- “foot;” cf. Skt. pat; Gk. pos, genitive podos; L. pes, genitive pedis; E. foot; Ger. Fuss; Fr. pied; PIE *pod-/*ped-.
Foru “down, downward; below, under, beneath; low,” Mid.Pers. frôt “down, downward;” O.Pers. fravata “forward, downward;” Skt. pravát- “a sloping path, the slope of a mountain.”

1. A downward slope, especially of a road.
   

2. To assign to a lower status; to minimize the importance of (Dictionary.com).

See also: → down; → grade.

1. A downward slope, especially of a road.
   

2. To assign to a lower status; to minimize the importance of (Dictionary.com).

See also: → down; → grade.

1. To transfer data from any other computer to one’s computer.
   

2. The act of downloading.

Etymology (EN): → down; → load.

Etymology (PE): Bârgereftan, literally “to take load,” from bâr, → load, + gereftan “to take,” → receiver; bârgiri, verbal noun of bârgereftan.

1. To transfer data from any other computer to one’s computer.
   

2. The act of downloading.

Etymology (EN): → down; → load.

Etymology (PE): Bârgereftan, literally “to take load,” from bâr, → load, + gereftan “to take,” → receiver; bârgiri, verbal noun of bârgereftan.

A scenario of galaxy formation whereby massive galaxies formed earlier in the history of the → Universe (i.e. at high → redshifts) and completed their → star formation process more rapidly than low-mass galaxies. This scenario contrasts with what might be expected from simple → hierarchical structure formation scenarios, which predict that large galaxies formed in more recent times through the
→ merging of small galaxies.

Etymology (EN): Downsizing, first suggested by Cowie et al. (1996, AJ 112, 839), from downsize (v.), is a new sense for this term. Its current main meaning in non astrophysical contexts is “to make in a smaller size, or become smaller in size (in particular in economic vocabulary, by reductions in personnel),” from → down + → size.

Etymology (PE): Bozorg-bé-kucak, literally “large to small,” from bozorg, → large, +bé “to” + kucak, → small.

A scenario of galaxy formation whereby massive galaxies formed earlier in the history of the → Universe (i.e. at high → redshifts) and completed their → star formation process more rapidly than low-mass galaxies. This scenario contrasts with what might be expected from simple → hierarchical structure formation scenarios, which predict that large galaxies formed in more recent times through the
→ merging of small galaxies.

Etymology (EN): Downsizing, first suggested by Cowie et al. (1996, AJ 112, 839), from downsize (v.), is a new sense for this term. Its current main meaning in non astrophysical contexts is “to make in a smaller size, or become smaller in size (in particular in economic vocabulary, by reductions in personnel),” from → down + → size.

Etymology (PE): Bozorg-bé-kucak, literally “large to small,” from bozorg, → large, +bé “to” + kucak, → small.

1. With or in the direction of the current of a stream. → upstream.
   

2. Of or pertaining to the latter part of a process or system.

Etymology (EN): → down; → stream.

Etymology (PE): Forud, → incidence; water, → water.

1. With or in the direction of the current of a stream. → upstream.
   

2. Of or pertaining to the latter part of a process or system.

Etymology (EN): → down; → stream.

Etymology (PE): Forud, → incidence; water, → water.