An Etymological Dictionary of Astronomy and Astrophysics

Etymology (EN): L. ara “fire altar,” from PIE as- “to burn”.

Etymology (PE): Âtašdân “a hearth, a fire-place; a movable coal grate,” from
âtaš “fire” (from Mid.Pers. âtaxš, âzar-, O.Pers. *âtar-, Av. âtar-, from Indo-Iranian *âtar-, compare with L. âter (feminine âtra) “black” (from “blackened by fire”); PIE *âter) + -dân suffix denoting recipient.

Etymology (EN): L. ara “fire altar,” from PIE as- “to burn”.

Etymology (PE): Âtašdân “a hearth, a fire-place; a movable coal grate,” from
âtaš “fire” (from Mid.Pers. âtaxš, âzar-, O.Pers. *âtar-, Av. âtar-, from Indo-Iranian *âtar-, compare with L. âter (feminine âtra) “black” (from “blackened by fire”); PIE *âter) + -dân suffix denoting recipient.

The astronomical activities that took place from the 8th to the 14th century in the Middle East, Central Asia, North Africa, and Moorish Spain.
Arab/Arabic is not meant as an ethnic but rather a linguistic term. In fact a large number of Non-Arab scholars, mainly Persians, Mongols, and Spanish people, wrote their works in Arabic. Even so, many astronomical works were also produced in the other languages of this civilization, especially Persian and in the later centuries Turkish. For example, the main → zijs were originally written in Persian, a notable example being the Zij of Ulugh Beg (c. A.D. 1394-1449), a landmark in precise observations before the Renaissance. Therefore, the term Arabic astronomy is misleading. It also creates a disparity with respect to Western scholars who wrote in Latin. The term “Latin astronomy” is meaningless and as far as these scholars are concerned, the Latin adjective is not specified. For example,
the expressions like “the Latin astronomer Copernicus,” “the Latin physicist Newton,” or “the Latin philosopher Leibniz” are not used. See also → Islamic astronomy.

See also: M.E. arabik, from O.Fr. arabique, from L. Arabicus; → astronomy.

The astronomical activities that took place from the 8th to the 14th century in the Middle East, Central Asia, North Africa, and Moorish Spain.
Arab/Arabic is not meant as an ethnic but rather a linguistic term. In fact a large number of Non-Arab scholars, mainly Persians, Mongols, and Spanish people, wrote their works in Arabic. Even so, many astronomical works were also produced in the other languages of this civilization, especially Persian and in the later centuries Turkish. For example, the main → zijs were originally written in Persian, a notable example being the Zij of Ulugh Beg (c. A.D. 1394-1449), a landmark in precise observations before the Renaissance. Therefore, the term Arabic astronomy is misleading. It also creates a disparity with respect to Western scholars who wrote in Latin. The term “Latin astronomy” is meaningless and as far as these scholars are concerned, the Latin adjective is not specified. For example,
the expressions like “the Latin astronomer Copernicus,” “the Latin physicist Newton,” or “the Latin philosopher Leibniz” are not used. See also → Islamic astronomy.

See also: M.E. arabik, from O.Fr. arabique, from L. Arabicus; → astronomy.

A → neutral point located at about 20° above the → antisolar point.

See also: Named for François Arago (1786-1853), French physicist; → point

A → neutral point located at about 20° above the → antisolar point.

See also: Named for François Arago (1786-1853), French physicist; → point

1. Based on individual will or choice rather than by reason or necessity.
   

   2. Math.: Undetermined; of unspecified value. → arbitrary constant.

Etymology (EN): M.E., from O.Fr. arbitraire or directly from L. arbitrarius “depending on the will, uncertain,” from → ad- “to” + baetere “to come, go.”

Etymology (PE): Kâmsar, literally “at one’s will,” from kâm “desire, wish; cause, reason,” → despite, + sar “person, individual,” originally “→ head.”

1. Based on individual will or choice rather than by reason or necessity.
   

   2. Math.: Undetermined; of unspecified value. → arbitrary constant.

Etymology (EN): M.E., from O.Fr. arbitraire or directly from L. arbitrarius “depending on the will, uncertain,” from → ad- “to” + baetere “to come, go.”

Etymology (PE): Kâmsar, literally “at one’s will,” from kâm “desire, wish; cause, reason,” → despite, + sar “person, individual,” originally “→ head.”

A constant quantity in → equations which takes various values but which remains unaffected by the changes in the values of the → variables of the equation.

Most → differential equations have more than one → solution. In general, the number of arbitrary constants of an ordinary differential equation is given by the → order of the highest → derivative.

See also: → arbitrary; → constant.

A constant quantity in → equations which takes various values but which remains unaffected by the changes in the values of the → variables of the equation.

Most → differential equations have more than one → solution. In general, the number of arbitrary constants of an ordinary differential equation is given by the → order of the highest → derivative.

See also: → arbitrary; → constant.

1. In → graph theory, a → rooted tree that has a natural orientation in which all → paths are directed away from the → root. More specifically, a → directed graph in which, for a → vertex u, called the → root, and any other vertex v, there is exactly one → directed path from u to v.
   

   2. Biology: The state of being branched, or treelike, in structure, appearance, growth, or other properties.

Etymology (EN): From Fr. arborescence, from → arborescent + → -ance.

Etymology (PE): Šâkedâri, nous from šâkedâr, → arborescent.

1. In → graph theory, a → rooted tree that has a natural orientation in which all → paths are directed away from the → root. More specifically, a → directed graph in which, for a → vertex u, called the → root, and any other vertex v, there is exactly one → directed path from u to v.
   

   2. Biology: The state of being branched, or treelike, in structure, appearance, growth, or other properties.

Etymology (EN): From Fr. arborescence, from → arborescent + → -ance.

Etymology (PE): Šâkedâri, nous from šâkedâr, → arborescent.

Having the shape or characteristics of a tree in growth, structure, or appearance.

Etymology (EN): From Fr. arborescent, from L. arborescent-, p.p. of arborescere “to grow into a tree,” from arbor, arboris “tree.”

Etymology (PE): Šâkedâr “having branches,” from šâké, from šâxé, → branch, + dâr “having, possessor,” from dâštan “to have, to possess,” → charged.

Having the shape or characteristics of a tree in growth, structure, or appearance.

Etymology (EN): From Fr. arborescent, from L. arborescent-, p.p. of arborescere “to grow into a tree,” from arbor, arboris “tree.”

Etymology (PE): Šâkedâr “having branches,” from šâké, from šâxé, → branch, + dâr “having, possessor,” from dâštan “to have, to possess,” → charged.

1. General: Something shaped like a → curve or → arch.
   

2. Math.: A → segment of a → circle.
   

3. Electricity: A continuous luminous → discharge across a gap between two → electrodes, as in an arc lamp. → electric arc.
   

4. Astro.: The apparent path of a celestial body above and below the horizon.

Etymology (EN): M.E. ark, from M.Fr. arc “bow,” from L. arcus “bow, arch” (cf. Goth. arhwazna “arrow,” O.E. earh), PIE *arqu- “bowed, curved.”

Etymology (PE): Kamân “arc, bow” from Mid.Pers. kamân, related to xam “curve,” cf. Breton kamm “curved, bent,” Gk. kampe “a corner, a joint,” L. campus “a field,”
Lith. kampus “corner,” PIE *kamb- “to bend, crook.”

1. General: Something shaped like a → curve or → arch.
   

2. Math.: A → segment of a → circle.
   

3. Electricity: A continuous luminous → discharge across a gap between two → electrodes, as in an arc lamp. → electric arc.
   

4. Astro.: The apparent path of a celestial body above and below the horizon.

Etymology (EN): M.E. ark, from M.Fr. arc “bow,” from L. arcus “bow, arch” (cf. Goth. arhwazna “arrow,” O.E. earh), PIE *arqu- “bowed, curved.”

Etymology (PE): Kamân “arc, bow” from Mid.Pers. kamân, related to xam “curve,” cf. Breton kamm “curved, bent,” Gk. kampe “a corner, a joint,” L. campus “a field,”
Lith. kampus “corner,” PIE *kamb- “to bend, crook.”

A unit of angular size equal to 1/60 of a degree.

See also: → arc; → minute.

A unit of angular size equal to 1/60 of a degree.

See also: → arc; → minute.

The apparent angular separation (→ elongation) between the → centers of the → Sun and the → Moon.

See also: → arc; → light.

The apparent angular separation (→ elongation) between the → centers of the → Sun and the → Moon.

See also: → arc; → light.

The difference in → right ascension between the → Sun and the → Moon,
measured in degrees.

See also: → arc; → separation.

The difference in → right ascension between the → Sun and the → Moon,
measured in degrees.

See also: → arc; → separation.

The → angular  → difference in → altitude between the → Sun and the → Moon.

See also: → arc; → vision.

The → angular  → difference in → altitude between the → Sun and the → Moon.

See also: → arc; → vision.

A unit of angular size equal to 1/3.600 of a degree.

See also: → arc; → second.

A unit of angular size equal to 1/3.600 of a degree.

See also: → arc; → second.

The spectrum produced by an atom or mixture of atoms as a result of vaporization within an electric arc generated between two electrodes.

See also: → arc; → spectrum.

The spectrum produced by an atom or mixture of atoms as a result of vaporization within an electric arc generated between two electrodes.

See also: → arc; → spectrum.

1. A curved structure, normally in the vertical plane, that spans an opening.
   

2. Any overhead curvature resembling an arch.
   → Arches cluster.

Etymology (EN): M.E. arch(e), from O.Fr. arche “arch of a bridge,”
from L. arcus “a bow,” → arc.

Etymology (PE): Taq “arch,” from tâk, contraction of târak, → vertex.

1. A curved structure, normally in the vertical plane, that spans an opening.
   

2. Any overhead curvature resembling an arch.
   → Arches cluster.

Etymology (EN): M.E. arch(e), from O.Fr. arche “arch of a bridge,”
from L. arcus “a bow,” → arc.

Etymology (PE): Taq “arch,” from tâk, contraction of târak, → vertex.

Any of the four vaulted structures in the foot: the internal (medial) longitudinal, the outer (lateral) longitudinal, and two transverse (Medical Dictionary, Farlex).

See also: → arch; → foot.

Any of the four vaulted structures in the foot: the internal (medial) longitudinal, the outer (lateral) longitudinal, and two transverse (Medical Dictionary, Farlex).

See also: → arch; → foot.

The study that deals with the astronomical knowledge
of prehistoric peoples (season events, calendars, observing sites, astronomical alignments) and its influence on their cultures and societies (mythologies, religions, life). Archaeoastronomy covers the intersection between astronomy and archaeology. Same as → astroarchaeology, megalithic astronomy.

Etymology (EN): Archeoastronomy, from L. archaeo-, archeo “ancient; earlier; primitive,” from Gk. arkhaio-, from
arkhaios “ancient” + → astronomy.

Etymology (PE): Bâstânaxtaršenâsi, from bâstân “ancient” + axtaršenâsi, → astronomy.

The study that deals with the astronomical knowledge
of prehistoric peoples (season events, calendars, observing sites, astronomical alignments) and its influence on their cultures and societies (mythologies, religions, life). Archaeoastronomy covers the intersection between astronomy and archaeology. Same as → astroarchaeology, megalithic astronomy.

Etymology (EN): Archeoastronomy, from L. archaeo-, archeo “ancient; earlier; primitive,” from Gk. arkhaio-, from
arkhaios “ancient” + → astronomy.

Etymology (PE): Bâstânaxtaršenâsi, from bâstân “ancient” + axtaršenâsi, → astronomy.

A prefix meaning “principal, prior, original, first, early” Same as archi-. → archetype.

Etymology (EN): From Gk. arkhe-, from arckhon “ruler,” noun use of p.p. of arkhein “to rule.”

Etymology (PE): Sar-, from sar “top, summit, the capital of a pillar,” → head.

A prefix meaning “principal, prior, original, first, early” Same as archi-. → archetype.

Etymology (EN): From Gk. arkhe-, from arckhon “ruler,” noun use of p.p. of arkhein “to rule.”

Etymology (PE): Sar-, from sar “top, summit, the capital of a pillar,” → head.

One of the three → Galactic center clusters supposed to be the densest young → massive star cluster in the Milky Way. It contains the richest collection of → O stars and → WN Wolf-Rayet stars in any cluster in the Galaxy, thus representing the largest collection of the most massive stars in the Galaxy. With its estimated age of 2-3 million years, the Arches cluster is the youngest of the massive clusters in the Galactic center. → Quintuplet cluster; → Central cluster (Figer et al. 2002, ApJ 581, 258; and 1999, ApJ 525, 750).

See also: Arches, from the presence of Galactic center thermal → arched filaments, about 100 → light-years in projection from the Galactic center (Morris & Yusef-Zadeh, 1985, AJ 90, 2511), from M.E. arche, O.Fr. arche “arch of a bridge,” from L. arcus, → arc; → cluster.

One of the three → Galactic center clusters supposed to be the densest young → massive star cluster in the Milky Way. It contains the richest collection of → O stars and → WN Wolf-Rayet stars in any cluster in the Galaxy, thus representing the largest collection of the most massive stars in the Galaxy. With its estimated age of 2-3 million years, the Arches cluster is the youngest of the massive clusters in the Galactic center. → Quintuplet cluster; → Central cluster (Figer et al. 2002, ApJ 581, 258; and 1999, ApJ 525, 750).

See also: Arches, from the presence of Galactic center thermal → arched filaments, about 100 → light-years in projection from the Galactic center (Morris & Yusef-Zadeh, 1985, AJ 90, 2511), from M.E. arche, O.Fr. arche “arch of a bridge,” from L. arcus, → arc; → cluster.

The original pattern or model from which all things of the same kind are copied or on which they are based; a model or first form; prototype (Dictionary.com).

See also: → arche-; → type.

The original pattern or model from which all things of the same kind are copied or on which they are based; a model or first form; prototype (Dictionary.com).

See also: → arche-; → type.

A body immersed totally or partially in a liquid is buoyed up by a force equal to the weight of the liquid displaced by the body. → buoyancy.

Etymology (EN): Archimedes of Syracuse (c. 287 BC - c. 212 BC), Greek mathematician and inventor; → principle.

Etymology (PE): Arašmidos altered form of Archimedes in classical Ar. texts; parvaz, → principle.

A body immersed totally or partially in a liquid is buoyed up by a force equal to the weight of the liquid displaced by the body. → buoyancy.

Etymology (EN): Archimedes of Syracuse (c. 287 BC - c. 212 BC), Greek mathematician and inventor; → principle.

Etymology (PE): Arašmidos altered form of Archimedes in classical Ar. texts; parvaz, → principle.

1. The art or practice of designing and building structures.
   

2. Computers: The arrangement of the various devices in a computer system or network. See also → software architecture.

Etymology (EN): M.E., from M.Fr. architecture, from L. architectura, from architectus “architect,” from Gk. arkhitekton “master builder, director of works,” from arkhi- “chief” + tekton “builder, carpenter,” → technique.

Etymology (PE): Mehrâzik, from mehrâz literally “chief mason,” from meh- “great, large,” → high, + râz “mason, builder” (Borhân-e Qâte’), from Mid.Pers. râz “builder, architect,” probably related to O.Pers. râs-, Av. râz- “to direct, set, put in line” (with many cognates in Pers., such as râst “straight, direct, true;”
raj, rak, râk, rezg (Lori), radé, râdé “line, rule, row,” rasté, râsté “row, a market with regular ranges of shops;” ris, risé “straight”); cf. Skt. raj- “to direct, stretch,” rjuyant- “walking straight;” Gk. orektos “stretched out;” L. regere “to lead straight, guide, rule,” p.p. rectus “right, straight;” Ger. recht; E. right; PIE base *reg- “move in a straight line,” hence, “to direct, rule;” + -ik, → -ics.

1. The art or practice of designing and building structures.
   

2. Computers: The arrangement of the various devices in a computer system or network. See also → software architecture.

Etymology (EN): M.E., from M.Fr. architecture, from L. architectura, from architectus “architect,” from Gk. arkhitekton “master builder, director of works,” from arkhi- “chief” + tekton “builder, carpenter,” → technique.

Etymology (PE): Mehrâzik, from mehrâz literally “chief mason,” from meh- “great, large,” → high, + râz “mason, builder” (Borhân-e Qâte’), from Mid.Pers. râz “builder, architect,” probably related to O.Pers. râs-, Av. râz- “to direct, set, put in line” (with many cognates in Pers., such as râst “straight, direct, true;”
raj, rak, râk, rezg (Lori), radé, râdé “line, rule, row,” rasté, râsté “row, a market with regular ranges of shops;” ris, risé “straight”); cf. Skt. raj- “to direct, stretch,” rjuyant- “walking straight;” Gk. orektos “stretched out;” L. regere “to lead straight, guide, rule,” p.p. rectus “right, straight;” Ger. recht; E. right; PIE base *reg- “move in a straight line,” hence, “to direct, rule;” + -ik, → -ics.

Any extensive record or collection of data.

Etymology (EN): Archive, from Fr. archives, from L. archivum, from Gk. arkheion “government house, town hall,” from arkhe “government,” from arkhein “to rule”.

Etymology (PE): Bâygâni, maybe from *pâygâni, from pây-, pâyidan “to watch, guard, take care, conserve” + -gân, suffix referring to group, collection, + -i, noun-forming suffix.

Any extensive record or collection of data.

Etymology (EN): Archive, from Fr. archives, from L. archivum, from Gk. arkheion “government house, town hall,” from arkhe “government,” from arkhein “to rule”.

Etymology (PE): Bâygâni, maybe from *pâygâni, from pây-, pâyidan “to watch, guard, take care, conserve” + -gân, suffix referring to group, collection, + -i, noun-forming suffix.

An angular measurement equal to 1/60 of a degree. It is denoted by the symbol ‘.

See also: → arc; → minute.

An angular measurement equal to 1/60 of a degree. It is denoted by the symbol ‘.

See also: → arc; → minute.

An angular measurement equal to 1/3600 of a degree or 1/60 of an arcminute. It is denoted by the symbol ‘’. There are 206,264.5’’ in a radian, so that 1’’ = 4.848 × 10^-6 radians.

See also: → arc; → second.

An angular measurement equal to 1/3600 of a degree or 1/60 of an arcminute. It is denoted by the symbol ‘’. There are 206,264.5’’ in a radian, so that 1’’ = 4.848 × 10^-6 radians.

See also: → arc; → second.

The north polar area, north of latitude 66° 33’ 8’’ N.

Etymology (EN): Arctic, from O.Fr. artique, from L. arcticus, from Gk. arktikos “of the north,” literally
“of the (northerly prominent constellation) Bear,” from arktos “bear” (cf. Av. arša-, Mod.Pers. xers, Tabari aš, Skt. rksa, L. ursus; PIE *rtko-).

Etymology (PE): Hudargân, from hudar, → north,

• -gân prefix denoting the direction.
  Šomâlgân, from šomâl “north,” from Ar. šemâl “north, left”+ -gân.

The north polar area, north of latitude 66° 33’ 8’’ N.

Etymology (EN): Arctic, from O.Fr. artique, from L. arcticus, from Gk. arktikos “of the north,” literally
“of the (northerly prominent constellation) Bear,” from arktos “bear” (cf. Av. arša-, Mod.Pers. xers, Tabari aš, Skt. rksa, L. ursus; PIE *rtko-).

Etymology (PE): Hudargân, from hudar, → north,

• -gân prefix denoting the direction.
  Šomâlgân, from šomâl “north,” from Ar. šemâl “north, left”+ -gân.

The fourth brightest star in the sky (V magnitude -0.06) lying in the constellation → Boötes at a distance of about 35 light-years. Arcturus is a red giant of spectral type K2 IIIp.

Etymology (EN): L. Arcturus, from Gk. Arktouros “guardian of the bear,” arktos “bear,” → Arctic + ouros “guardian, watcher”.

Etymology (PE): Xersbân “guardian of the bear,” from xers “bear” (Mid.Pers. xirs, Av. arša-, cognate with Gk. arktos, Skt. rksa, L. ursus; PIE *rtko-) + -bân suffix meaning “watcher, keeper, guard”.
Ar. Semâk-e râmeh.

The fourth brightest star in the sky (V magnitude -0.06) lying in the constellation → Boötes at a distance of about 35 light-years. Arcturus is a red giant of spectral type K2 IIIp.

Etymology (EN): L. Arcturus, from Gk. Arktouros “guardian of the bear,” arktos “bear,” → Arctic + ouros “guardian, watcher”.

Etymology (PE): Xersbân “guardian of the bear,” from xers “bear” (Mid.Pers. xirs, Av. arša-, cognate with Gk. arktos, Skt. rksa, L. ursus; PIE *rtko-) + -bân suffix meaning “watcher, keeper, guard”.
Ar. Semâk-e râmeh.

A particular extent of space or surface; the scope of a concept, operation, or activity.

Etymology (EN): The etymology is not clear; perhaps akin to L. arere “to be dry” → arid.

Etymology (PE): Pahné “area, field,” from pahn “broad, wide” (Mid.Pers. pah(a)n, Av. pathana- “broad, wide, spacious,” probably related to perethav- “broad, wide,” Skt. prthav-, Gk. platus; PIE *plat- “to spread”) + noun forming suffix -é.

A particular extent of space or surface; the scope of a concept, operation, or activity.

Etymology (EN): The etymology is not clear; perhaps akin to L. arere “to be dry” → arid.

Etymology (PE): Pahné “area, field,” from pahn “broad, wide” (Mid.Pers. pah(a)n, Av. pathana- “broad, wide, spacious,” probably related to perethav- “broad, wide,” Skt. prthav-, Gk. platus; PIE *plat- “to spread”) + noun forming suffix -é.

The study of the surface features of Mars; the geography of Mars.

Etymology (EN): Areography, from Gk. Ares “Mars” + → -graphy.

Etymology (PE): Bahrâm-negâri, from Bahrâm “Mars” + -negâri→ -graphy.

The study of the surface features of Mars; the geography of Mars.

Etymology (EN): Areography, from Gk. Ares “Mars” + → -graphy.

Etymology (PE): Bahrâm-negâri, from Bahrâm “Mars” + -negâri→ -graphy.

The study of the origin, history, and structure of Mars; the geology
of Mars.

Etymology (EN): Areology, from Gk. Ares “Mars” + → -logy.

Etymology (PE): Bahrâm-šenâsi, from Bahrâm “Mars” + -šenâsi→ -logy.

The study of the origin, history, and structure of Mars; the geology
of Mars.

Etymology (EN): Areology, from Gk. Ares “Mars” + → -logy.

Etymology (PE): Bahrâm-šenâsi, from Bahrâm “Mars” + -šenâsi→ -logy.

A geometrical representation of → complex numbers, which like the → Cartesian coordinates, uses two reference perpendicular axes. The horizontal axis represents the → real number part of the number and the perpendicular axis the → imaginary number part.

See also: Named after Jean Robert Argand (1768-1822), a Swiss mathematician, who introduced this representation; → diagram.

A geometrical representation of → complex numbers, which like the → Cartesian coordinates, uses two reference perpendicular axes. The horizontal axis represents the → real number part of the number and the perpendicular axis the → imaginary number part.

See also: Named after Jean Robert Argand (1768-1822), a Swiss mathematician, who introduced this representation; → diagram.

A technique to estimate the brightness of a → variable star. It involves comparing the variable with a sequence of neighboring stars of slightly different → magnitudes.

See also: Friedrich Wilhelm Argelander (1799-1875), German astronomer. His most important work was his compilation of the Bonner Durchmusterung; → method.

A technique to estimate the brightness of a → variable star. It involves comparing the variable with a sequence of neighboring stars of slightly different → magnitudes.

See also: Friedrich Wilhelm Argelander (1799-1875), German astronomer. His most important work was his compilation of the Bonner Durchmusterung; → method.

An extensive constellation, one of the 48 constellations known to Greeks, representing the ship of Argonauts. It was divided in 18th century into the constellations → Carina, → Puppis, and → Vela.

Etymology (EN): The ship in which Jason sailed in search of the Golden Fleece.

Etymology (PE): Kašti “ship,” from Mid.Pers. kaštik.

An extensive constellation, one of the 48 constellations known to Greeks, representing the ship of Argonauts. It was divided in 18th century into the constellations → Carina, → Puppis, and → Vela.

Etymology (EN): The ship in which Jason sailed in search of the Golden Fleece.

Etymology (PE): Kašti “ship,” from Mid.Pers. kaštik.

A generally reddish matter that settles from a liquid, especially from wine.
Same as → tartar.

Etymology (EN): M.E. argul, argoile, from M.Fr. argoil, from L. argilla “argil.”

Etymology (PE): Lerd ou lert “the sediment of liquids, dregs, lees” (Dehxodâ).

A generally reddish matter that settles from a liquid, especially from wine.
Same as → tartar.

Etymology (EN): M.E. argul, argoile, from M.Fr. argoil, from L. argilla “argil.”

Etymology (PE): Lerd ou lert “the sediment of liquids, dregs, lees” (Dehxodâ).

A → chemical element which occurs as a colorless, odorless, and tasteless gas in the atmosphere (of which it constitutes 0.94% by volume) and in some volcanic gases; symbol Ar. → Atomic number 18; → atomic weight 39.948; → melting point -189.2°C; → boiling points -185.7°C.

See also: Argon, from Gk. neutral of argos “inactive, idle, lazy,” from negation prefix → a- + ergon “work,” → energy. It was discovered in 1895 by the Scottish chemist William Ramsay and the English physicist Robert John Strutt (Lord Rayleigh) in liquified atmospheric air.

A → chemical element which occurs as a colorless, odorless, and tasteless gas in the atmosphere (of which it constitutes 0.94% by volume) and in some volcanic gases; symbol Ar. → Atomic number 18; → atomic weight 39.948; → melting point -189.2°C; → boiling points -185.7°C.

See also: Argon, from Gk. neutral of argos “inactive, idle, lazy,” from negation prefix → a- + ergon “work,” → energy. It was discovered in 1895 by the Scottish chemist William Ramsay and the English physicist Robert John Strutt (Lord Rayleigh) in liquified atmospheric air.

To put forth reasons for or against.

See also: → argument.

To put forth reasons for or against.

See also: → argument.

1. General: A discussion involving differing points of view; debate; a process of reasoning; series of reasons.
   

2a) Math.: The → independent variable of a
→ function.

2b) Math.: The → angle of a → complex number measured from the positive horizontal axis.

3. Astro.: → argument of periapsis, → argument of perigee, → argument of perihelion.
   

4a) Logic: A sequence of → propositions with one or more → premises and a → conclusion.
Arguments are usually divided into two kinds, → deductive and → inductive.

4b) Logic: A → propositional symbol (→ variable or → constant) taken by a → predicate in an → atomic wff.

Etymology (EN): M.E., from M.Fr., from L. argmentum, from arguere “to make clear.” Compare with L. argentum “silver,” Gk. argos “white,” arguron “silver,” Av. auruša- “white” (Mid.Pers. arus “white, bright”), Av.
ərəzata- “silver,” Skt. arjuna- “white, shining,” rajata- “silver,” Mod.Pers. arziz “silvery metal tin;”
PIE *arg- “to shine, be white, bright, clear.”

Etymology (PE): Âruzmân, from Av. āroc- “to enlighten, make light,” Av. raocah- “light, luminous; daylight;” Skt. roka- “brightness, light,” cognate with Gk. leukos “white, clear;” L. lux “light” (also lumen, luna);
PIE *leuk- “light, brightness” + noun forming suffix -mân.

1. General: A discussion involving differing points of view; debate; a process of reasoning; series of reasons.
   

2a) Math.: The → independent variable of a
→ function.

2b) Math.: The → angle of a → complex number measured from the positive horizontal axis.

3. Astro.: → argument of periapsis, → argument of perigee, → argument of perihelion.
   

4a) Logic: A sequence of → propositions with one or more → premises and a → conclusion.
Arguments are usually divided into two kinds, → deductive and → inductive.

4b) Logic: A → propositional symbol (→ variable or → constant) taken by a → predicate in an → atomic wff.

Etymology (EN): M.E., from M.Fr., from L. argmentum, from arguere “to make clear.” Compare with L. argentum “silver,” Gk. argos “white,” arguron “silver,” Av. auruša- “white” (Mid.Pers. arus “white, bright”), Av.
ərəzata- “silver,” Skt. arjuna- “white, shining,” rajata- “silver,” Mod.Pers. arziz “silvery metal tin;”
PIE *arg- “to shine, be white, bright, clear.”

Etymology (PE): Âruzmân, from Av. āroc- “to enlighten, make light,” Av. raocah- “light, luminous; daylight;” Skt. roka- “brightness, light,” cognate with Gk. leukos “white, clear;” L. lux “light” (also lumen, luna);
PIE *leuk- “light, brightness” + noun forming suffix -mân.

The angular distance between the → ascending node of an object orbiting a → primary and its periapsis measured from the primary. Argument of periapsis is measured in the → orbital plane in the direction of motion. It is one of the → orbital elements. See also → argument of perigee, → argument of perihelion.

See also: → argument; → perigee.

The angular distance between the → ascending node of an object orbiting a → primary and its periapsis measured from the primary. Argument of periapsis is measured in the → orbital plane in the direction of motion. It is one of the → orbital elements. See also → argument of perigee, → argument of perihelion.

See also: → argument; → perigee.

The angular distance between the → ascending node of an object orbiting the Earth and its perigee, measured from the Earth. See also: → argument of perihelion, → argument of periapsis.

See also: → argument; → perigee.

The angular distance between the → ascending node of an object orbiting the Earth and its perigee, measured from the Earth. See also: → argument of perihelion, → argument of periapsis.

See also: → argument; → perigee.

The angular distance between the → ascending node of an object orbiting the Sun and its perihelion. Argument of perihelion is measured in the → orbital plane with respect to the Sun and in the direction of motion. It is one of the → orbital elements and usually shown with the symbol ω. See also: → argument of perigee, → argument of periapsis.

See also: → argument; → perihelion.

The angular distance between the → ascending node of an object orbiting the Sun and its perihelion. Argument of perihelion is measured in the → orbital plane with respect to the Sun and in the direction of motion. It is one of the → orbital elements and usually shown with the symbol ω. See also: → argument of perigee, → argument of periapsis.

See also: → argument; → perihelion.

The presentation and elaboration of an argument or arguments.

See also: Noun from → argument.

The presentation and elaboration of an argument or arguments.

See also: Noun from → argument.

1. Fond of or given to argument and dispute.
   

2. Of or characterized by argument; controversial.

See also: → argue; → -ive

1. Fond of or given to argument and dispute.
   

2. Of or characterized by argument; controversial.

See also: → argue; → -ive

Lacking sufficient water or rainfall.

Etymology (EN): L. aridus, from arere “to be dry, i.e. burnt up”;
compare with Gk. azaleos “dry,” PIE *as- “to burn, glow”.

Etymology (PE): Kamâb, from Mod.P. kam “little, few, deficient, scarce”

• âb “water”.

Lacking sufficient water or rainfall.

Etymology (EN): L. aridus, from arere “to be dry, i.e. burnt up”;
compare with Gk. azaleos “dry,” PIE *as- “to burn, glow”.

Etymology (PE): Kamâb, from Mod.P. kam “little, few, deficient, scarce”

• âb “water”.

A measure of the degree to which a climate lacks effective moisture.

Etymology (EN): Aridity, noun from → arid.

Etymology (PE): Kamâbi, noun from amâbi, → arid.

A measure of the degree to which a climate lacks effective moisture.

Etymology (EN): Aridity, noun from → arid.

Etymology (PE): Kamâbi, noun from amâbi, → arid.

A satellite of → Uranus discovered by Lassell in 1851. It is orbiting at a mean distance of 192,000 kilometers with a period of 2.52 days.

Etymology (EN): Ariel, a spirit in William Shakespeare’s The Tempest.

A satellite of → Uranus discovered by Lassell in 1851. It is orbiting at a mean distance of 192,000 kilometers with a period of 2.52 days.

Etymology (EN): Ariel, a spirit in William Shakespeare’s The Tempest.

The Ram. A constellation of the → Zodiac, representing a ram (R.A. = 2h 30m, Dec. = +13 deg). Its brightest star is → Hamal (α Arietis). Abbreviation: Ari; genitive form: Arietis.

Etymology (EN): L. aries “ram,” perhaps akin to Gk. eriphos
“a kid, a young goat,” O.Ir. heirp “she-goat;” cf. Lith. erytis, O.C.S. jarici, Arm. oroj “lamb.”

Etymology (PE): Barré “ram, sheep; Aries” from Mid.Pers. warrag “lamb, ram; Aries,” compare with Av. varənâ- “wool,” Skt. urana, urabhra “wool-beared = ram,” from urna “wool,” L. vervex “a wether, sheep”.

The Ram. A constellation of the → Zodiac, representing a ram (R.A. = 2h 30m, Dec. = +13 deg). Its brightest star is → Hamal (α Arietis). Abbreviation: Ari; genitive form: Arietis.

Etymology (EN): L. aries “ram,” perhaps akin to Gk. eriphos
“a kid, a young goat,” O.Ir. heirp “she-goat;” cf. Lith. erytis, O.C.S. jarici, Arm. oroj “lamb.”

Etymology (PE): Barré “ram, sheep; Aries” from Mid.Pers. warrag “lamb, ram; Aries,” compare with Av. varənâ- “wool,” Skt. urana, urabhra “wool-beared = ram,” from urna “wool,” L. vervex “a wether, sheep”.

Put in modern notation, if α and β are acute angles and if β <α, then sin α / sin β <α / β < tan α / tan β. Aristarchus probably used this inequality to show that the Sun is between 18 and 20 times as far from the Earth as the Moon is.

See also: Aristarchus of Samos (c.310-c.230 BC); → inequality.

Put in modern notation, if α and β are acute angles and if β <α, then sin α / sin β <α / β < tan α / tan β. Aristarchus probably used this inequality to show that the Sun is between 18 and 20 times as far from the Earth as the Moon is.

See also: Aristarchus of Samos (c.310-c.230 BC); → inequality.

Any of the four main → proposition forms treated in Aristotle’s → syllogism:

The A form (universal affirmative): All P’s are Q’s,

The E form (universal negative): No P’s are Q’s,

The I form (particular affirmative): Some P’s are Q’s, and

The O form (particular negative) Some P’s are not Q’s.

See also: Greek philosopher Aristotle (384-322 BC); → form.

Any of the four main → proposition forms treated in Aristotle’s → syllogism:

The A form (universal affirmative): All P’s are Q’s,

The E form (universal negative): No P’s are Q’s,

The I form (particular affirmative): Some P’s are Q’s, and

The O form (particular negative) Some P’s are not Q’s.

See also: Greek philosopher Aristotle (384-322 BC); → form.

A branch of mathematics that deals usually with integers, rational numbers, real numbers, or complex numbers under addition, subtraction, multiplication, and division. See also → compute, → computation, → count, → calculate, → calculus, → mathematics, → statistics.

Etymology (EN): O.Fr. arsmetique, from M.L. arithmetica, from Gk. arithmetike (tekhne) “(art, skill) of numbers,” from arithmos “number.”

Etymology (PE): Hesâb, from Ar. hisab.

A branch of mathematics that deals usually with integers, rational numbers, real numbers, or complex numbers under addition, subtraction, multiplication, and division. See also → compute, → computation, → count, → calculate, → calculus, → mathematics, → statistics.

Etymology (EN): O.Fr. arsmetique, from M.L. arithmetica, from Gk. arithmetike (tekhne) “(art, skill) of numbers,” from arithmos “number.”

Etymology (PE): Hesâb, from Ar. hisab.

Of n numbers a₁, a₂, …, a_n, the quantity defined as:
(a₁ + a₂ + … + a_n)/n.

See also: → arithmetic; → mean.

Of n numbers a₁, a₂, …, a_n, the quantity defined as:
(a₁ + a₂ + … + a_n)/n.

See also: → arithmetic; → mean.

A → sequence of n numbers or quantities such that the difference between any two successive terms is a constant. In particular, if a is the first term, the nth term is a + (n - 1)d, where d is the constant. Also called → arithmetic sequence.

See also: → arithmetic; → progression.

A → sequence of n numbers or quantities such that the difference between any two successive terms is a constant. In particular, if a is the first term, the nth term is a + (n - 1)d, where d is the constant. Also called → arithmetic sequence.

See also: → arithmetic; → progression.

→ arithmetic progression.

See also: → arithmetic; → sequence.

→ arithmetic progression.

See also: → arithmetic; → sequence.

1. Each of the upper limbs of the human body, especially the part between the → shoulder and the → wrist.
   

2. The upper limb from the shoulder to the → elbow.
   

3. A slender part of a structure projecting from a main part, such as a → spiral arm. → Orion Arm;
   → Perseus Arm; → Scutum-Crux Arm.

Etymology (EN): M.E. arm, from O.E. earm “arm,” from P.Gmc. *armaz (cf. M.Du., Ger. Arm, O.N. armr, O.Fris. erm), from PIE base *ar- “to fit, join;” cf.
Mod.Pers. arm, as below.

Etymology (PE): 1) Ârm (Dehxodâ, Steingass) “arm, from the elbow to the shoulder;” Av. arma-, arəmo- “arm;” cf. Ossetic ärm “hand;” Armenian armuku “elbow;” Skt. irma- “arm;”
Gk. arthron “a joint;” L. armus “shoulder;” cognate with E. arm, as above.

2. Bâzu, → upper arm.

1. Each of the upper limbs of the human body, especially the part between the → shoulder and the → wrist.
   

2. The upper limb from the shoulder to the → elbow.
   

3. A slender part of a structure projecting from a main part, such as a → spiral arm. → Orion Arm;
   → Perseus Arm; → Scutum-Crux Arm.

Etymology (EN): M.E. arm, from O.E. earm “arm,” from P.Gmc. *armaz (cf. M.Du., Ger. Arm, O.N. armr, O.Fris. erm), from PIE base *ar- “to fit, join;” cf.
Mod.Pers. arm, as below.

Etymology (PE): 1) Ârm (Dehxodâ, Steingass) “arm, from the elbow to the shoulder;” Av. arma-, arəmo- “arm;” cf. Ossetic ärm “hand;” Armenian armuku “elbow;” Skt. irma- “arm;”
Gk. arthron “a joint;” L. armus “shoulder;” cognate with E. arm, as above.

2. Bâzu, → upper arm.

An ancient instrument, used since ancient times until the Middle ages and later, to determine positions of celestial bodies. It consisted of an assemblage of rings, all circles of the same sphere, designed to represent the positions of the important circles of the celestial sphere.

Etymology (EN): L. armillarius, from armilla “arm ring, bracelet,” from armus “arm” + → sphere.

Etymology (PE): Zâtolhelaq from Ar. “multi-ringed,” from zât “holder, keeper”

• helaq “rings,” from halqah “ring.”

An ancient instrument, used since ancient times until the Middle ages and later, to determine positions of celestial bodies. It consisted of an assemblage of rings, all circles of the same sphere, designed to represent the positions of the important circles of the celestial sphere.

Etymology (EN): L. armillarius, from armilla “arm ring, bracelet,” from armus “arm” + → sphere.

Etymology (PE): Zâtolhelaq from Ar. “multi-ringed,” from zât “holder, keeper”

• helaq “rings,” from halqah “ring.”

1. An agreement between opposing armies to stop fighting for a particular time, especially in order to discuss possible peace; truce
   

   2. A formal agreement, especially between nations, to end combat.

Etymology (EN): From Fr. armistice, from L. arma “arms” + -stitium, from sistere “to cause to stand,” → solstice.

Etymology (PE): Nâjangân, literally “state of no war,” from nâ- “no, not,” → un-, + jang, → war,

• -ân suffix of time and place.

1. An agreement between opposing armies to stop fighting for a particular time, especially in order to discuss possible peace; truce
   

   2. A formal agreement, especially between nations, to end combat.

Etymology (EN): From Fr. armistice, from L. arma “arms” + -stitium, from sistere “to cause to stand,” → solstice.

Etymology (PE): Nâjangân, literally “state of no war,” from nâ- “no, not,” → un-, + jang, → war,

• -ân suffix of time and place.

The → peak luminosity of a → Type Ia supernova is proportional to the rate of → radioactive decay and hence directly proportional to the mass of ⁵⁶Ni.

See also: Arnett, W. D. 1982, ApJ, 253, 785; → rule.

The → peak luminosity of a → Type Ia supernova is proportional to the rate of → radioactive decay and hence directly proportional to the mass of ⁵⁶Ni.

See also: Arnett, W. D. 1982, ApJ, 253, 785; → rule.

Chemistry: Of, relating to, or containing the six-carbon ring typical of the benzene (C₆H₆) series and related organic groups.

See also: M.E. aromatyk, from M.Fr. aromatique, from L. aromaticus, from Gk. aromatikos, from aroma “seasoning, sweet spice,” of unknown origin.

Chemistry: Of, relating to, or containing the six-carbon ring typical of the benzene (C₆H₆) series and related organic groups.

See also: M.E. aromatyk, from M.Fr. aromatique, from L. aromaticus, from Gk. aromatikos, from aroma “seasoning, sweet spice,” of unknown origin.

An organic compound which contains benzene rings in its structure. The simplest is therefore benzene (C₆H₆). Aromatic compounds have a planar ring of atoms linked by alternate single and double bounds.

See also: → aromatic; → compound.

An organic compound which contains benzene rings in its structure. The simplest is therefore benzene (C₆H₆). Aromatic compounds have a planar ring of atoms linked by alternate single and double bounds.

See also: → aromatic; → compound.

A family of strong infrared emission bands at 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 μm which are widely observed in a large variety of objects, such as → H II regions, → reflection nebulae, → planetary nebulae, and the → diffuse interstellar medium of our galaxy and other galaxies. Solar system objects, such as carbonaceous → meteorites and → interplanetary dust particles are also known to display these features. They are suggested to be due to → polycyclic aromatic hydrocarbons.

See also: → aromatic; → infrared; → band.

A family of strong infrared emission bands at 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 μm which are widely observed in a large variety of objects, such as → H II regions, → reflection nebulae, → planetary nebulae, and the → diffuse interstellar medium of our galaxy and other galaxies. Solar system objects, such as carbonaceous → meteorites and → interplanetary dust particles are also known to display these features. They are suggested to be due to → polycyclic aromatic hydrocarbons.

See also: → aromatic; → infrared; → band.

1. To set in a rank or row. To put in order.
   

2. Music: To adapt for other instruments or voices.

Etymology (EN): From M.E. arayngen, from M.Fr. arangier, from O.Fr. arengier, from a- “to,” → ad-, + rangier “set in a row,” from rang, → rank.

Etymology (PE): Rezgidan “to set in a row,” from Lori rezg “row,” related to râst, → right, Av. rāz- “to direct, draw a line;” probably ultimately from Proto-Ir. *Hrazaka- “row.”

1. To set in a rank or row. To put in order.
   

2. Music: To adapt for other instruments or voices.

Etymology (EN): From M.E. arayngen, from M.Fr. arangier, from O.Fr. arengier, from a- “to,” → ad-, + rangier “set in a row,” from rang, → rank.

Etymology (PE): Rezgidan “to set in a row,” from Lori rezg “row,” related to râst, → right, Av. rāz- “to direct, draw a line;” probably ultimately from Proto-Ir. *Hrazaka- “row.”

The act of arranging or being arranged. Result or manner of arranging.

See also: Verbal noun of → arrange.

The act of arranging or being arranged. Result or manner of arranging.

See also: Verbal noun of → arrange.

1. A system of telescopes coupled together, using → interferometric techniques, to increase the angular resolution or the sensitivity.
   

2. A two-dimensional detector comprising a large number of identical, individual detectors that can be used simultaneously, e.g. a → CCD.
   

3. A series of numbers or symbols arranged in some geometric pattern, as in a matrix.

Etymology (EN): Array, from M.E. arraien, from Anglo-Norman arraier, from V.L. *arredare.

Etymology (PE): Ârast “set in order,” from ârastan, ârâstan “to set in order,” Mid.Pers. ârây-, ârâstan, from â- + Av. râd- “to make ready, prepare;” PIE *ar- “to fit together.”

1. A system of telescopes coupled together, using → interferometric techniques, to increase the angular resolution or the sensitivity.
   

2. A two-dimensional detector comprising a large number of identical, individual detectors that can be used simultaneously, e.g. a → CCD.
   

3. A series of numbers or symbols arranged in some geometric pattern, as in a matrix.

Etymology (EN): Array, from M.E. arraien, from Anglo-Norman arraier, from V.L. *arredare.

Etymology (PE): Ârast “set in order,” from ârastan, ârâstan “to set in order,” Mid.Pers. ârây-, ârâstan, from â- + Av. râd- “to make ready, prepare;” PIE *ar- “to fit together.”

An important relationship in physical chemistry that combines the concepts of → activation energy and the → Maxwell-Boltzmann distribution law. It is expressed by: k = Ae^-E_a/(RT), where k is the chemical → reaction rate, E_a is the activation energy, R is the → gas constant, and T is → temperature.

See also: Named for Svante Arrhenius (1859-1927), Swedish chemist and physicist who suggested the relationship in 1889.

An important relationship in physical chemistry that combines the concepts of → activation energy and the → Maxwell-Boltzmann distribution law. It is expressed by: k = Ae^-E_a/(RT), where k is the chemical → reaction rate, E_a is the activation energy, R is the → gas constant, and T is → temperature.

See also: Named for Svante Arrhenius (1859-1927), Swedish chemist and physicist who suggested the relationship in 1889.

The precise time at which the gamma burst photons hit a
detector. Measuring the time difference between the arrival time of the photons at different telescopes separated by known distances permits to determine the burst direction.

Etymology (EN): Arrival, n. from arrive + → -al. Arrive, from O.Fr. ariver “to come to land,” from V.L. *arripare “to touch the shore,” from L. ad ripam “to the shore,” from → ad “to” + ripa “shore;” → time.

Etymology (PE): Zamân, → time; raseš n. from rasidan “to arrive,” Mid.Pers. rasitan, O.Pers./Av. rasa- present stem of ar- “to move, go or come toward,” cf. Skt. ar-, rcchati.

The precise time at which the gamma burst photons hit a
detector. Measuring the time difference between the arrival time of the photons at different telescopes separated by known distances permits to determine the burst direction.

Etymology (EN): Arrival, n. from arrive + → -al. Arrive, from O.Fr. ariver “to come to land,” from V.L. *arripare “to touch the shore,” from L. ad ripam “to the shore,” from → ad “to” + ripa “shore;” → time.

Etymology (PE): Zamân, → time; raseš n. from rasidan “to arrive,” Mid.Pers. rasitan, O.Pers./Av. rasa- present stem of ar- “to move, go or come toward,” cf. Skt. ar-, rcchati.

A slender, straight, generally pointed missile or weapon made to be shot from a bow and equipped with feathers at the end of the shaft near the → nock, for controlling flight (Dictionary.com). → Sagitta.

Etymology (EN): M.E. arewe, arwe, O.E. earh, possibly borrowed from O.N. ör;
ultimately from PIE *arku- “bow and/or arrow,” → arc.

Etymology (PE): Peykân “arrow, javelin” (cognate with afkan-, afkandan “to throw, cast away,” parâkan-, parâkandan “to scatter, to disperse”),
ultimately from Proto-Iranian *paiti-kan- “to throw against,” from *paiti- “against, opposite, back” (cf. Mod.Pers. pâd- “against, contrary to;” Mid.Pers. pât-; O.Pers. paity “against, back, opposite to, toward, face to face, in front of;” Av. paiti; Skt. práti “toward, against, again, back, in return, opposite;” Pali pati-; Gk. proti, pros “face to face with, toward, in addition to, near;” PIE *proti) + *kan- “to throw.”

A slender, straight, generally pointed missile or weapon made to be shot from a bow and equipped with feathers at the end of the shaft near the → nock, for controlling flight (Dictionary.com). → Sagitta.

Etymology (EN): M.E. arewe, arwe, O.E. earh, possibly borrowed from O.N. ör;
ultimately from PIE *arku- “bow and/or arrow,” → arc.

Etymology (PE): Peykân “arrow, javelin” (cognate with afkan-, afkandan “to throw, cast away,” parâkan-, parâkandan “to scatter, to disperse”),
ultimately from Proto-Iranian *paiti-kan- “to throw against,” from *paiti- “against, opposite, back” (cf. Mod.Pers. pâd- “against, contrary to;” Mid.Pers. pât-; O.Pers. paity “against, back, opposite to, toward, face to face, in front of;” Av. paiti; Skt. práti “toward, against, again, back, in return, opposite;” Pali pati-; Gk. proti, pros “face to face with, toward, in addition to, near;” PIE *proti) + *kan- “to throw.”

A silver-gray black metallic → chemical element which is very brittle; symbol As. → Atomic number 33;
→ atomic weight 74.9216; → boiling point 613.0 °C (sublimation);
→ valence -3, 0, +3, or +5. The uncombined element is not considered poisonous, but many of its compounds are extremely so, and are used in medicine and for destroying pests. Its longest-lived radioactive → isotope, ⁷³As, has a → half-life of 80.3 days.

Etymology (EN): M.E. arsenik, from O.Fr. arsenic, from L. arsenicum, from Gk. arsenikon “arsenic,” adapted from Syriac (al) zarniqa “arsenic,” from Mid.Pers. zarnik “arsenic,” literally “gold-colored,” probably because of the lemon-yellow color of arsenic trisulphide (Mod.Pers. zarnix, zarni “arsenic”), from zarr, zar “gold” (+ -ik→ -ic); Av. zaranya-, zarənu- “gold;” O.Pers. daraniya- “gold;” cf. Skt. hiranya- “gold;” also Av. zaray-, zairi- “yellow, green;” Mod.Pers. zard “yellow;” Skt. hari- “yellow, green;” Gk. khloe literally “young green shoot;” L. helvus “yellowish, bay;” Rus. zeltyj “yellow;” P.Gmc. *gelwaz; Du. geel; Ger. gelb; E. yellow.

Etymology (PE): Ârsenik, loan from Fr., as above.

A silver-gray black metallic → chemical element which is very brittle; symbol As. → Atomic number 33;
→ atomic weight 74.9216; → boiling point 613.0 °C (sublimation);
→ valence -3, 0, +3, or +5. The uncombined element is not considered poisonous, but many of its compounds are extremely so, and are used in medicine and for destroying pests. Its longest-lived radioactive → isotope, ⁷³As, has a → half-life of 80.3 days.

Etymology (EN): M.E. arsenik, from O.Fr. arsenic, from L. arsenicum, from Gk. arsenikon “arsenic,” adapted from Syriac (al) zarniqa “arsenic,” from Mid.Pers. zarnik “arsenic,” literally “gold-colored,” probably because of the lemon-yellow color of arsenic trisulphide (Mod.Pers. zarnix, zarni “arsenic”), from zarr, zar “gold” (+ -ik→ -ic); Av. zaranya-, zarənu- “gold;” O.Pers. daraniya- “gold;” cf. Skt. hiranya- “gold;” also Av. zaray-, zairi- “yellow, green;” Mod.Pers. zard “yellow;” Skt. hari- “yellow, green;” Gk. khloe literally “young green shoot;” L. helvus “yellowish, bay;” Rus. zeltyj “yellow;” P.Gmc. *gelwaz; Du. geel; Ger. gelb; E. yellow.

Etymology (PE): Ârsenik, loan from Fr., as above.

The process or product of human activity which is the expression of creativity and/or imagination that appeals to the senses or emotions.

Etymology (EN): From O.Fr. art, from L. artem, (nominative ars) “art, skill, craft;” from PIE base *ar- “to fit, join;” cf. Mod.Pers. arm “arm, from the elbow to the shoulder;” Av. arma-, arəmo- “arm;” Skt. irma- “arm;”
Gk. arthron “a joint;” L. armus “shoulder.”

Etymology (PE): Honar, from Mid.Pers. hunar “skill, ability, virtue, manliness;” O.Pers. hūnarā- “abilities, skills;” Av. hunara- “ability, skill”; cf. Skt. sūnára- “powerful, joyous, beautiful;” Proto-Iranian *Hnar- “to be able, strong.”

The process or product of human activity which is the expression of creativity and/or imagination that appeals to the senses or emotions.

Etymology (EN): From O.Fr. art, from L. artem, (nominative ars) “art, skill, craft;” from PIE base *ar- “to fit, join;” cf. Mod.Pers. arm “arm, from the elbow to the shoulder;” Av. arma-, arəmo- “arm;” Skt. irma- “arm;”
Gk. arthron “a joint;” L. armus “shoulder.”

Etymology (PE): Honar, from Mid.Pers. hunar “skill, ability, virtue, manliness;” O.Pers. hūnarā- “abilities, skills;” Av. hunara- “ability, skill”; cf. Skt. sūnára- “powerful, joyous, beautiful;” Proto-Iranian *Hnar- “to be able, strong.”

A blood vessel that conveys blood from the heart to any part of the body (Dictionary.com).

Etymology (EN): M.E. arterie, O.Fr. artaire, from L. arteria, from Gk. arteria “windpipe,” also “an artery,” as distinct from a vein; related to aeirein “to raise.”

Etymology (PE): Sorxrag, literally “red vessel,” from sorx, → red, + rag, → vessel.

A blood vessel that conveys blood from the heart to any part of the body (Dictionary.com).

Etymology (EN): M.E. arterie, O.Fr. artaire, from L. arteria, from Gk. arteria “windpipe,” also “an artery,” as distinct from a vein; related to aeirein “to raise.”

Etymology (PE): Sorxrag, literally “red vessel,” from sorx, → red, + rag, → vessel.

1. A nonfictional prose composition usually forming an independent part of a publication in a magazine.
   
2. A written document devoted to a scientific research and appearing in specialized journal.

Etymology (EN): Article, from O.Fr. article, from L. articulus, diminutive of artus “a joint”.

Etymology (PE): Vetâr, from Kurd. witâr “article, speech,” from witten “to speak, say,” from wit-; cf. Pers. vât “letter, word,” vâžé “word;” Av. vac- “to speak, say;” Proto-Iranian *uac- “to say, speak;” → letter.

1. A nonfictional prose composition usually forming an independent part of a publication in a magazine.
   
2. A written document devoted to a scientific research and appearing in specialized journal.

Etymology (EN): Article, from O.Fr. article, from L. articulus, diminutive of artus “a joint”.

Etymology (PE): Vetâr, from Kurd. witâr “article, speech,” from witten “to speak, say,” from wit-; cf. Pers. vât “letter, word,” vâžé “word;” Av. vac- “to speak, say;” Proto-Iranian *uac- “to say, speak;” → letter.

1. An object made by a human being, typically one of cultural or historical interest.
   

2. Something observed in a scientific investigation or experiment that is not naturally present but occurs as a result of the preparative or investigative procedure (OxfordDictionary.com).

Etymology (EN): From It. artefatto, from L. arte “by skill” (ablative of ars “→ art”) + factum “thing made,” from facere “to make, do,” → -fy.

Etymology (PE): Dasâc “hand made,” from das variant of dast, → hand, + sâc, variant of sâz-, sâxtan, → agree.

1. An object made by a human being, typically one of cultural or historical interest.
   

2. Something observed in a scientific investigation or experiment that is not naturally present but occurs as a result of the preparative or investigative procedure (OxfordDictionary.com).

Etymology (EN): From It. artefatto, from L. arte “by skill” (ablative of ars “→ art”) + factum “thing made,” from facere “to make, do,” → -fy.

Etymology (PE): Dasâc “hand made,” from das variant of dast, → hand, + sâc, variant of sâz-, sâxtan, → agree.

Not occurring naturally; produced by man.

Etymology (EN): M.E., from O.Fr., from L. artificialis “belonging to art,” from artificium “craftsmanship.”

Etymology (PE): Sâxtegi “artificial,” from sâxtan “to build, to make,” → structure.

Not occurring naturally; produced by man.

Etymology (EN): M.E., from O.Fr., from L. artificialis “belonging to art,” from artificium “craftsmanship.”

Etymology (PE): Sâxtegi “artificial,” from sâxtan “to build, to make,” → structure.

A shallow flat vessel filled with → mercury or some other viscous → liquid used in special → sextant for measuring altitudes of celestial bodies at sea in the absence of a → visible horizon.

See also: → artificial; → horizon.

A shallow flat vessel filled with → mercury or some other viscous → liquid used in special → sextant for measuring altitudes of celestial bodies at sea in the absence of a → visible horizon.

See also: → artificial; → horizon.

An artificially created language system for international communication or for a specific intellectual or scientific purpose. Examples include Esperanto, computer programing languages, → symbolic logic, and → tensor analysis.

See also: → artificial; → language.

An artificially created language system for international communication or for a specific intellectual or scientific purpose. Examples include Esperanto, computer programing languages, → symbolic logic, and → tensor analysis.

See also: → artificial; → language.

Any light other than that which proceeds from the heavenly bodies.

See also: → artificial; → light.

Any light other than that which proceeds from the heavenly bodies.

See also: → artificial; → light.

A man-made equipment that orbits around Earth or a solar system body.

See also: → artificial; → satellite.

A man-made equipment that orbits around Earth or a solar system body.

See also: → artificial; → satellite.

In → adaptive optics, a point source created on the sky by means of a laser beam in order to correct for the → atmospheric turbulence. A laser tuned to the wavelength of 589 nm will excite sodium atoms at an altitude of ~ 100 km in the Earth’s atmosphere, producing an artificial “star.”

See also: → artificial; → star.

In → adaptive optics, a point source created on the sky by means of a laser beam in order to correct for the → atmospheric turbulence. A laser tuned to the wavelength of 589 nm will excite sodium atoms at an altitude of ~ 100 km in the Earth’s atmosphere, producing an artificial “star.”

See also: → artificial; → star.