An Etymological Dictionary of Astronomy and Astrophysics

1. Burning gas or vapor, as from wood or coal, that is undergoing combustion; a portion of ignited gas or vapor.
   

2. Any flame-like condition; glow; inflamed condition (Dictionary.com).

Etymology (EN): M.E. flaume, variant of flaumbe from Anglo-French flaume, flaumbe “a flame;” O.Fr. flambe, from L. flammula “small flame,” diminutive of flamma “flame, blazing fire,” from PIE *bhleg- “to shine, flash,” from root *bhel- (1) “to shine, flash, burn.”

Etymology (PE): Âyež, from (Dehxodâ) âyež “flame,” variants âyiž, âyežé, ižak, of unknown origin.

1. Burning gas or vapor, as from wood or coal, that is undergoing combustion; a portion of ignited gas or vapor.
   

2. Any flame-like condition; glow; inflamed condition (Dictionary.com).

Etymology (EN): M.E. flaume, variant of flaumbe from Anglo-French flaume, flaumbe “a flame;” O.Fr. flambe, from L. flammula “small flame,” diminutive of flamma “flame, blazing fire,” from PIE *bhleg- “to shine, flash,” from root *bhel- (1) “to shine, flash, burn.”

Etymology (PE): Âyež, from (Dehxodâ) âyež “flame,” variants âyiž, âyežé, ižak, of unknown origin.

A stellar designation system in which each star is assigned a number followed by the Latin genitive of its corresponding → constellation, such as → 61 Cygni and 82 Eridani. Compare with the → Bayer designation.

See also: Named after John Flamsteed (1646-1719), founder of the Greenwich Observatory, and the first astronomer royal of England, who introduced this system in his catalog Historia Coelestis Britannica (1725); → designation.

A stellar designation system in which each star is assigned a number followed by the Latin genitive of its corresponding → constellation, such as → 61 Cygni and 82 Eridani. Compare with the → Bayer designation.

See also: Named after John Flamsteed (1646-1719), founder of the Greenwich Observatory, and the first astronomer royal of England, who introduced this system in his catalog Historia Coelestis Britannica (1725); → designation.

1. A sudden blaze or burst of fire or light.
   

2. → solar flare.

Etymology (EN): From v. flare “to spread out,” said of hair, a ship’s sides, etc., of unknown origin.

Etymology (PE): Âlâv, “blaze, fire,” variants alow, Borujerdi elew “fire,” Garkuyeyi alôv “flame,” Hamadâni elow “flame,” Lori alô “flame,” Tabari aluk “flame, spark,” Torbat-Heydariyeyi alow “flame;”
cf. Gk. aithos “fire,” aitho “to kindle;” Skt. edh- “to set alight, kindle,” édha-, édhas- “firewood;” Av. aēsma- “firewood;” Mod.Pers. hizom, himé “firewood;” PIE base *aidh- “to burn,” *aidhos- “fire.”

1. A sudden blaze or burst of fire or light.
   

2. → solar flare.

Etymology (EN): From v. flare “to spread out,” said of hair, a ship’s sides, etc., of unknown origin.

Etymology (PE): Âlâv, “blaze, fire,” variants alow, Borujerdi elew “fire,” Garkuyeyi alôv “flame,” Hamadâni elow “flame,” Lori alô “flame,” Tabari aluk “flame, spark,” Torbat-Heydariyeyi alow “flame;”
cf. Gk. aithos “fire,” aitho “to kindle;” Skt. edh- “to set alight, kindle,” édha-, édhas- “firewood;” Av. aēsma- “firewood;” Mod.Pers. hizom, himé “firewood;” PIE base *aidh- “to burn,” *aidhos- “fire.”

A member of a class of dwarf stars that undergoes sudden, intense outbursts of light (mean amplitude about 0.5-0.6 mag).

See also: → flare; → star.

A member of a class of dwarf stars that undergoes sudden, intense outbursts of light (mean amplitude about 0.5-0.6 mag).

See also: → flare; → star.

A model of → accretion disk around a → pre-main sequence star or a → protostar in which the ratio of the disk thickness to the distance from the star increases outward. Current models of the irradiation of flared disks by stellar radiation predict that a central hole is created around the young star due to the evaporation of dust by the stellar radiation. The inner rim of the disk, at 0.5 to 1 AU from the star, is irradiated by the star “frontally” (at 90° angle). The heat produced by the irradiation causes the inner rim to puff up. A part of the disk, from about 1 to 6 AU, lies in the shadow of the puffed-up inner rim. The surface layers in this region do not receive stellar photons directly. Therefore, there is no significant heating of the disk midplane by reprocessed stellar flux from the disk surface. The midplane temperatures in the shadowed part of the disk are governed by the → near infrared emission of the inner rim, scattering of stellar light by dust particles outside the disk plane, and radial diffusion which exchanges energy between adjacent slabs.
As for the outer parts of the disk, the surface is irradiated by the central star thanks to the outward widening of the disk. These parts remain flared, because the absorbed stellar flux is partially emitted toward the midplane, keeping the internal temperatures high enough to push the surface layers up. The flattened-disk model explains the observed
→ spectral energy distribution of some objects
such as HD 179218. It also accounts for the observed strong → far-infrared, → excess, strong → PAH emission, and strong [O I] emission. Compare with → self-shadowed disk. See also → protoplanetary disk.

Etymology (EN): Flared, from flare “to spread gradually outward, as the end of a trumpet, having a gradual increase in width,” of unknown origin; → disk.

Etymology (PE): Gerdé, → disk; borun-gošâ “opening outward,” from borun “out, the outside” (Mid.Pers. bêron, from bê “outside, out, away” + rôn “side, direction;” Av. ravan- “(course of a) river”) + gošâ stem of gošâdan, gošudan “to open;” Mid.Pers. wišâdan “to open, let free;” Khotanese hiyā “bound;” O.Pers. višta “untied, loosend;” vištāspa- (personal name) “with loosened horses;” Av. višta “untied,” hita- “fastened, tied on;” cf. Skt. sā- “to bind, fasten,” syáti “binds.”

A model of → accretion disk around a → pre-main sequence star or a → protostar in which the ratio of the disk thickness to the distance from the star increases outward. Current models of the irradiation of flared disks by stellar radiation predict that a central hole is created around the young star due to the evaporation of dust by the stellar radiation. The inner rim of the disk, at 0.5 to 1 AU from the star, is irradiated by the star “frontally” (at 90° angle). The heat produced by the irradiation causes the inner rim to puff up. A part of the disk, from about 1 to 6 AU, lies in the shadow of the puffed-up inner rim. The surface layers in this region do not receive stellar photons directly. Therefore, there is no significant heating of the disk midplane by reprocessed stellar flux from the disk surface. The midplane temperatures in the shadowed part of the disk are governed by the → near infrared emission of the inner rim, scattering of stellar light by dust particles outside the disk plane, and radial diffusion which exchanges energy between adjacent slabs.
As for the outer parts of the disk, the surface is irradiated by the central star thanks to the outward widening of the disk. These parts remain flared, because the absorbed stellar flux is partially emitted toward the midplane, keeping the internal temperatures high enough to push the surface layers up. The flattened-disk model explains the observed
→ spectral energy distribution of some objects
such as HD 179218. It also accounts for the observed strong → far-infrared, → excess, strong → PAH emission, and strong [O I] emission. Compare with → self-shadowed disk. See also → protoplanetary disk.

Etymology (EN): Flared, from flare “to spread gradually outward, as the end of a trumpet, having a gradual increase in width,” of unknown origin; → disk.

Etymology (PE): Gerdé, → disk; borun-gošâ “opening outward,” from borun “out, the outside” (Mid.Pers. bêron, from bê “outside, out, away” + rôn “side, direction;” Av. ravan- “(course of a) river”) + gošâ stem of gošâdan, gošudan “to open;” Mid.Pers. wišâdan “to open, let free;” Khotanese hiyā “bound;” O.Pers. višta “untied, loosend;” vištāspa- (personal name) “with loosened horses;” Av. višta “untied,” hita- “fastened, tied on;” cf. Skt. sā- “to bind, fasten,” syáti “binds.”

A Sudden, brief burst of light. In particular, → green flash.

Etymology (EN): From M.E. flasshen “to sprinkle, splash,” from flasken, probably imitative.

Etymology (PE): Deraxš, present stem of deraxšidan “to shine, radiate,” from raxš “lightening, reflection of light,” raxšidan “to shine, flash,” O.Pers. raucah-, Av. raocah- “light” (cf. Skt. roka- “brightness, light,” Gk. leukos “white, clear,” L. lux “light” (also lumen, luna), E. light, Ger. Licht, Fr. lumière;
PIE base *leuk- “light, brightness”); cognate with Mod.Pers. words
ruz “day,” rowšan “bright, clear,” foruq “light,” and afruxtan “to light, kindle.”

A Sudden, brief burst of light. In particular, → green flash.

Etymology (EN): From M.E. flasshen “to sprinkle, splash,” from flasken, probably imitative.

Etymology (PE): Deraxš, present stem of deraxšidan “to shine, radiate,” from raxš “lightening, reflection of light,” raxšidan “to shine, flash,” O.Pers. raucah-, Av. raocah- “light” (cf. Skt. roka- “brightness, light,” Gk. leukos “white, clear,” L. lux “light” (also lumen, luna), E. light, Ger. Licht, Fr. lumière;
PIE base *leuk- “light, brightness”); cognate with Mod.Pers. words
ruz “day,” rowšan “bright, clear,” foruq “light,” and afruxtan “to light, kindle.”

The spectrum of the solar → chromosphere obtained during a → solar eclipse in the instant before or after → totality. In the flash
spectrum the usual solar → absorption lines are replaced with
bright → emission lines. This is because in that very short interval only the → photosphere is eclipsed by the Moon, and not the chromosphere. The American astronomer Charles A. Young was the first to observe it during the the solar eclipse of 1870 (December 22) in Spain.

See also: The flash designation comes from the fact that the change from dark-line to bright-line spectrum is very rapid; → flash; → spectrum.

The spectrum of the solar → chromosphere obtained during a → solar eclipse in the instant before or after → totality. In the flash
spectrum the usual solar → absorption lines are replaced with
bright → emission lines. This is because in that very short interval only the → photosphere is eclipsed by the Moon, and not the chromosphere. The American astronomer Charles A. Young was the first to observe it during the the solar eclipse of 1870 (December 22) in Spain.

See also: The flash designation comes from the fact that the change from dark-line to bright-line spectrum is very rapid; → flash; → spectrum.

Level and horizontal, without any slope; even and smooth, without any bumps or hollows.
See also:
→ flat manifold, → flat Universe, → flat-field, → flatness problem.

Etymology (EN): Flat, from O.N. flatr, from P.Gmc. *flataz (cf. O.H.G. flaz “flat, level,” O.E. flet, O.H.G. flezzi “floor”), perhaps from PIE *pla- (cf. Gk. platys “broad, flat;” Av. pərətu- “broad, wide;” Skt. prthu- “broad, wide, large”).

Etymology (PE): Taxt “flat;” Mid.Pers. taxtag “tablet, plank, (chess)board.”

Level and horizontal, without any slope; even and smooth, without any bumps or hollows.
See also:
→ flat manifold, → flat Universe, → flat-field, → flatness problem.

Etymology (EN): Flat, from O.N. flatr, from P.Gmc. *flataz (cf. O.H.G. flaz “flat, level,” O.E. flet, O.H.G. flezzi “floor”), perhaps from PIE *pla- (cf. Gk. platys “broad, flat;” Av. pərətu- “broad, wide;” Skt. prthu- “broad, wide, large”).

Etymology (PE): Taxt “flat;” Mid.Pers. taxtag “tablet, plank, (chess)board.”

A manifold with a → Riemannian metric that has
→ zero → curvature.

See also: → flat; → manifold.

A manifold with a → Riemannian metric that has
→ zero → curvature.

See also: → flat; → manifold.

A galactic → rotation curve in which the → rotation velocity is constant in the outer parts. The flat component is preceded by a rising curve that shows solid body rotation in the very center of the → galaxy. A flat rotation curve implies that the mass is still increasing linearly with radius. See also → dark matter.

See also: → flat; → rotation; → curve.

A galactic → rotation curve in which the → rotation velocity is constant in the outer parts. The flat component is preceded by a rising curve that shows solid body rotation in the very center of the → galaxy. A flat rotation curve implies that the mass is still increasing linearly with radius. See also → dark matter.

See also: → flat; → rotation; → curve.

A Universe where the → geometry is → Euclidean, i.e. parallel lines remain parallel when extended into the distance and the sum of the interior angles of a triangle is 180°. The → space-time in a flat Universe has a null → curvature constant, k = 0. See also → closed Universe, → open Universe.

See also: → flat; → universe.

A Universe where the → geometry is → Euclidean, i.e. parallel lines remain parallel when extended into the distance and the sum of the interior angles of a triangle is 180°. The → space-time in a flat Universe has a null → curvature constant, k = 0. See also → closed Universe, → open Universe.

See also: → flat; → universe.

Exposure of a diffuse and uniform source in order to calibrate the non-uniformity of an imaging detector such as a CCD.

Etymology (EN): → flat; → field.

Etymology (PE): Meydân, → field; taxt, → flat.

Exposure of a diffuse and uniform source in order to calibrate the non-uniformity of an imaging detector such as a CCD.

Etymology (EN): → flat; → field.

Etymology (PE): Meydân, → field; taxt, → flat.

The observed fact that the → geometry of the → Universe is very nearly flat, in other words its density is very close to the → critical density. This would be an extreme coincidence because a → flat Universe is a special case. Many attempts have been made to explain the flatness problem, and modern theories now include the idea of → inflation.

See also: → flat; → problem.

The observed fact that the → geometry of the → Universe is very nearly flat, in other words its density is very close to the → critical density. This would be an extreme coincidence because a → flat Universe is a special case. Many attempts have been made to explain the flatness problem, and modern theories now include the idea of → inflation.

See also: → flat; → problem.

11 Taste, especially the distinctive taste of something as it is experienced in the mouth. A particular quality noticeable in a thing (Dictionary.com).

2. Any of the six labels given to the distinct kinds of → quark: up, down, strange, charm, bottom, and top.
   

3. → neutrino flavor.

Etymology (EN): M.E., from O.Fr. flaor “smell, odor; action of smelling, sense of smell,” probably from V.L. flator “odor,” literally “that which blows,” in L. “blower,” from flareQ “to blow, puff,” which is cognate with O.E. blawan, → blow.

Etymology (PE): Câšni “taste; taste by way of a sample; quality,” related to
cašidan, caš- “to taste,” câšt “breakfast,” cašté “bait;”
Mid.Pers. câšt “meal,” câšnig “taste;” cf. Skt. cas- “to eat;” Proto-Ir. caš- “to eat, to drink; to drip.”

11 Taste, especially the distinctive taste of something as it is experienced in the mouth. A particular quality noticeable in a thing (Dictionary.com).

2. Any of the six labels given to the distinct kinds of → quark: up, down, strange, charm, bottom, and top.
   

3. → neutrino flavor.

Etymology (EN): M.E., from O.Fr. flaor “smell, odor; action of smelling, sense of smell,” probably from V.L. flator “odor,” literally “that which blows,” in L. “blower,” from flareQ “to blow, puff,” which is cognate with O.E. blawan, → blow.

Etymology (PE): Câšni “taste; taste by way of a sample; quality,” related to
cašidan, caš- “to taste,” câšt “breakfast,” cašté “bait;”
Mid.Pers. câšt “meal,” câšnig “taste;” cf. Skt. cas- “to eat;” Proto-Ir. caš- “to eat, to drink; to drip.”

Two rules used to assist in remembering the relative directions of the magnetic field, current, and motion in electrical machines, using one’s fingers. The right hand refers to generators, the left hand to motors. The three directions are represented by the thumb (for force or motion), forefinger (for field), and second finger (for current), all held at right angles to each other.

See also: Devised by the British physicist and electrical engineer John Ambrose Fleming (1849-1945).

Two rules used to assist in remembering the relative directions of the magnetic field, current, and motion in electrical machines, using one’s fingers. The right hand refers to generators, the left hand to motors. The three directions are represented by the thumb (for force or motion), forefinger (for field), and second finger (for current), all held at right angles to each other.

See also: Devised by the British physicist and electrical engineer John Ambrose Fleming (1849-1945).

1. To bend or be bent.
   

   2. Of a material, to be capable of warping or bending and then reverting to shape (OxfordDictionaries.com).

Etymology (EN): Probably a back-formation from → flexible, from L. flexus, p.p. of flectere “to bend, turn.”

Etymology (PE): Caftidan, caftan “to bend, incline,” cafté “curved, bent,” of unknown origin.

1. To bend or be bent.
   

   2. Of a material, to be capable of warping or bending and then reverting to shape (OxfordDictionaries.com).

Etymology (EN): Probably a back-formation from → flexible, from L. flexus, p.p. of flectere “to bend, turn.”

Etymology (PE): Caftidan, caftan “to bend, incline,” cafté “curved, bent,” of unknown origin.

1. The quality of bending easily without breaking.
   

   2. The ability to be easily modified.

See also: → flexible; → -ity.

1. The quality of bending easily without breaking.
   

   2. The ability to be easily modified.

See also: → flexible; → -ity.

Capable of being bent easily without breaking.

See also: → flex + -ible, variant of → -able.

Capable of being bent easily without breaking.

See also: → flex + -ible, variant of → -able.

1. The act of bending, the state of being bent.
   

   2. The position that a limb assumes when it is bent.

See also: → flex; → -tion.

1. The act of bending, the state of being bent.
   

   2. The position that a limb assumes when it is bent.

See also: → flex; → -tion.

The action of bending or curving, or the condition of being bent or curved.

See also: → flex + suffix -ure.

The action of bending or curving, or the condition of being bent or curved.

See also: → flex + suffix -ure.

The act, manner, or power of flying.

Etymology (EN): O.E. flyht “a flying, flight,” from P.Gmc. *flukhtiz (cf. Ger. Flucht).

Etymology (PE): Parvâz, from Mid.Pers. parwâz; Av. pāirivāza- “overrunning,” from pāiri- “over (of space), from” + vāza- from vaz- “to fly, float; to drive;” cf. Skt. vah-, vahati. Also Mid.Pers. vâz “jump, flight,” Mod.Pers. Lori, Gilaki, Tabari vâz “jump, leap.”

The act, manner, or power of flying.

Etymology (EN): O.E. flyht “a flying, flight,” from P.Gmc. *flukhtiz (cf. Ger. Flucht).

Etymology (PE): Parvâz, from Mid.Pers. parwâz; Av. pāirivāza- “overrunning,” from pāiri- “over (of space), from” + vāza- from vaz- “to fly, float; to drive;” cf. Skt. vah-, vahati. Also Mid.Pers. vâz “jump, flight,” Mod.Pers. Lori, Gilaki, Tabari vâz “jump, leap.”

A basic type of optical glass containing lead oxide and a smaller amount of potassium, characterized by its brilliance, clarity, and durability. It has a high → dispersion relative to its → refractive index, as compared to, e.g. → crown glass. Flint glass is sometimes used as the diverging lens component of an → achromatic lens. It is also used in the manufacture of table glassware.

See also: Flint, because it was originally made of calcined flints,
from M.E., O.E.; cf. M.Du. vlint, O.H.G. flins, Dan. flint; Gk. plinthos “brick, tile.”

A basic type of optical glass containing lead oxide and a smaller amount of potassium, characterized by its brilliance, clarity, and durability. It has a high → dispersion relative to its → refractive index, as compared to, e.g. → crown glass. Flint glass is sometimes used as the diverging lens component of an → achromatic lens. It is also used in the manufacture of table glassware.

See also: Flint, because it was originally made of calcined flints,
from M.E., O.E.; cf. M.Du. vlint, O.H.G. flins, Dan. flint; Gk. plinthos “brick, tile.”

A galaxy that has short segments of patchy spiral structure so that the disk appears like the fleece of a sheep. Examples: NGC 2841 and NGC 5055.

Etymology (EN): From L. floccus “flock of wool” + -ulent; → spiral galaxy.

Etymology (PE): Kahkešân, → galaxy; mârpic, → spiral; pašmin “woolly, woollen,” from pašm “wool” (Mid.Pers. pašm “wool;” Av. pašna- “eyelash, eyelid;” cp. Skt. páksman- “eyelashes;” Gk. pekos “wool, fleece,” pek(t)ein “to comb, pluck;” Lith. pešti “to pluck;” O.N. fax “mane”).

A galaxy that has short segments of patchy spiral structure so that the disk appears like the fleece of a sheep. Examples: NGC 2841 and NGC 5055.

Etymology (EN): From L. floccus “flock of wool” + -ulent; → spiral galaxy.

Etymology (PE): Kahkešân, → galaxy; mârpic, → spiral; pašmin “woolly, woollen,” from pašm “wool” (Mid.Pers. pašm “wool;” Av. pašna- “eyelash, eyelid;” cp. Skt. páksman- “eyelashes;” Gk. pekos “wool, fleece,” pek(t)ein “to comb, pluck;” Lith. pešti “to pluck;” O.N. fax “mane”).

The overflowing of the normal confines of a stream or other body of water, or the accumulation of water over areas that are not normally submerged.

Etymology (EN): O.E. flod “a flowing of water, river, sea,” from P.Gmc. *flothuz (cf. M.Du. vloet, Ger. Flut), from PIE *plo-/*pleu- “flow, float” (cf. Gk. ploein “to float, swim”).

Etymology (PE): Laf “flood,” from Lori, Kordi, Malâyeri, lé in Tabari, variants
lur, lây “flood” [Mo’in, Dehxodâ];
cf. Gk. louein “to wash;” L. luere “to wash;”
Bret. laouer “trough;” PIE *lou- “to wash.” Seyl from Ar.

The overflowing of the normal confines of a stream or other body of water, or the accumulation of water over areas that are not normally submerged.

Etymology (EN): O.E. flod “a flowing of water, river, sea,” from P.Gmc. *flothuz (cf. M.Du. vloet, Ger. Flut), from PIE *plo-/*pleu- “flow, float” (cf. Gk. ploein “to float, swim”).

Etymology (PE): Laf “flood,” from Lori, Kordi, Malâyeri, lé in Tabari, variants
lur, lây “flood” [Mo’in, Dehxodâ];
cf. Gk. louein “to wash;” L. luere “to wash;”
Bret. laouer “trough;” PIE *lou- “to wash.” Seyl from Ar.

1. That part of a room, hallway, or the like, that forms its lower enclosing surface and upon which one walks.
   

2. A level, supporting surface in any structure (Dictionary.com).

Etymology (EN): M.E. flor, from O.E. flor (cf. M.Du. vloer, M.H.G. vluor, Ger. Flur “field, meadow”), from PIE *plaros, from *pele- “flat; to spread.”

Etymology (PE): Kaf “floor; plain ground.”

1. That part of a room, hallway, or the like, that forms its lower enclosing surface and upon which one walks.
   

2. A level, supporting surface in any structure (Dictionary.com).

Etymology (EN): M.E. flor, from O.E. flor (cf. M.Du. vloer, M.H.G. vluor, Ger. Flur “field, meadow”), from PIE *plaros, from *pele- “flat; to spread.”

Etymology (PE): Kaf “floor; plain ground.”

An → asteroid family that includes → Gaspra. The group has about 819 members and orbits between 2.17 and 2.33 → astronomical units from the Sun.

See also: → Flora; → family.

An → asteroid family that includes → Gaspra. The group has about 819 members and orbits between 2.17 and 2.33 → astronomical units from the Sun.

See also: → Flora; → family.

1. The act or state of remaining on the surface of a liquid. → buoyancy.
   

2. The process of separating different materials, especially minerals, by agitating a pulverized mixture of the materials with water, oil, and chemicals based on their tendency to sink in, or float on.

Etymology (EN): From float, from M.E. floten,  O.E. flotian (cf. O.N. flota, M.Du. vloten), akin to fleet + -ation.

Etymology (PE): Šenâvari “flotation,” from šenâvar “that swims, floats,” from šenâ “swimming;” Mid.Pers. šnâz “swim,” šnâzidan “to swim;” Av. snā- “to wash, swim;” cf. Skt. snā- “to bathe, to wash;” L. nare, natare “to swim” (Fr. nage, nager, natation; Sp.nadar, natacion).

1. The act or state of remaining on the surface of a liquid. → buoyancy.
   

2. The process of separating different materials, especially minerals, by agitating a pulverized mixture of the materials with water, oil, and chemicals based on their tendency to sink in, or float on.

Etymology (EN): From float, from M.E. floten,  O.E. flotian (cf. O.N. flota, M.Du. vloten), akin to fleet + -ation.

Etymology (PE): Šenâvari “flotation,” from šenâvar “that swims, floats,” from šenâ “swimming;” Mid.Pers. šnâz “swim,” šnâzidan “to swim;” Av. snā- “to wash, swim;” cf. Skt. snā- “to bathe, to wash;” L. nare, natare “to swim” (Fr. nage, nager, natation; Sp.nadar, natacion).

1a) Moving along in a → stream; going as in a stream.

1b) A → dynamical system that evolves continuously with time.

1c) The transference of energy.

2. The corresponding verb.

Etymology (EN): O.E. flowan, from P.Gmc. *flo- (cf. Du. vloeien “to flow,” O.H.G. flouwen “to rinse, wash”), probably from PIE *pleu- “to flow, float” (cf. Skt. plavate “navigates, swims,” plavayati “overflows;” Gk. plyno “I wash,” pleo “swim, go by sea;” L. pluere “to rain;” Arm. helum “I pour;”
Lith. pilu “to pour out”).

Etymology (PE): 1) Tacân, from tac- variant tâz- present stem of tacidan, tâxtan, tâzidan “to run; to hasten; to assault,”

• noun and adj. suffix -ân. Related to the first component are
  Mod.Pers. tajan name of a river (initially “flowing, streaming, stream”), tâzi “swift (greyhound),” tak “running, rush,” from
  Mid.Pers. tâz-, tâxtan “to flow, to cause to walk,” tc- “to flow, to walk,” tag “running, attack,” tâzig “swift, fast;”
  Khotanese ttajs- “to flow, to walk;” Av. tac- “to run, to flow,” taciāp- “flowing water,” tacinti (3pl.pers.act.) “to flow,”
  tacar- “course,” tacan “current, streaming;” cf. Skt. tak- “to rush, to hurry,” takti “runs;” O.Ir. tech- “to flow;” Lith. teketi “to walk, to flow;” O.C.S. tešti “to walk, to hurry;” Tokharian B cake “river;” PIE base *tek^w- “to run; to flow.”
  

2. Verbal form.

1a) Moving along in a → stream; going as in a stream.

1b) A → dynamical system that evolves continuously with time.

1c) The transference of energy.

2. The corresponding verb.

Etymology (EN): O.E. flowan, from P.Gmc. *flo- (cf. Du. vloeien “to flow,” O.H.G. flouwen “to rinse, wash”), probably from PIE *pleu- “to flow, float” (cf. Skt. plavate “navigates, swims,” plavayati “overflows;” Gk. plyno “I wash,” pleo “swim, go by sea;” L. pluere “to rain;” Arm. helum “I pour;”
Lith. pilu “to pour out”).

Etymology (PE): 1) Tacân, from tac- variant tâz- present stem of tacidan, tâxtan, tâzidan “to run; to hasten; to assault,”

• noun and adj. suffix -ân. Related to the first component are
  Mod.Pers. tajan name of a river (initially “flowing, streaming, stream”), tâzi “swift (greyhound),” tak “running, rush,” from
  Mid.Pers. tâz-, tâxtan “to flow, to cause to walk,” tc- “to flow, to walk,” tag “running, attack,” tâzig “swift, fast;”
  Khotanese ttajs- “to flow, to walk;” Av. tac- “to run, to flow,” taciāp- “flowing water,” tacinti (3pl.pers.act.) “to flow,”
  tacar- “course,” tacan “current, streaming;” cf. Skt. tak- “to rush, to hurry,” takti “runs;” O.Ir. tech- “to flow;” Lith. teketi “to walk, to flow;” O.C.S. tešti “to walk, to hurry;” Tokharian B cake “river;” PIE base *tek^w- “to run; to flow.”
  

2. Verbal form.

Same as → streamline.

See also: → flow; → line.

Same as → streamline.

See also: → flow; → line.

The amount of a substance, specifically a → fluid, moving across a specified unit → area in a given amount of → time.

See also: → flow; → rate.

The amount of a substance, specifically a → fluid, moving across a specified unit → area in a given amount of → time.

See also: → flow; → rate.

Same as → stream tube.

See also: → flow; → tube.

Same as → stream tube.

See also: → flow; → tube.

The ability of a body of matter (liquid, gas, loose particulate solid) to flow.

Etymology (EN): From flowable, adj. from → flow

• → -able + → -ity.

Etymology (PE): Tacandegi, from tacandé (originally tacandag),
agent noun of tacidan, → flow, + noun suffix -i.

The ability of a body of matter (liquid, gas, loose particulate solid) to flow.

Etymology (EN): From flowable, adj. from → flow

• → -able + → -ity.

Etymology (PE): Tacandegi, from tacandé (originally tacandag),
agent noun of tacidan, → flow, + noun suffix -i.

To change continually; to shift back and forth; vary irregularly; to rise and fall in or as if in waves.

Etymology (EN): From L. fluctuationem (nom. fluctuatio), from fluctuare “to undulate,” from fluctus “wave,” from p.p. of fluere “to flow.”

Etymology (PE): Verbal form of oftâxiz, → fluctuation.

To change continually; to shift back and forth; vary irregularly; to rise and fall in or as if in waves.

Etymology (EN): From L. fluctuationem (nom. fluctuatio), from fluctuare “to undulate,” from fluctus “wave,” from p.p. of fluere “to flow.”

Etymology (PE): Verbal form of oftâxiz, → fluctuation.

Continual rise and fall.

Etymology (EN): Verbal noun of → fluctuate.

Etymology (PE): Oftâxiz “fall and rise,” from oft “fall”
stem of oftâdan “to fall” (Mid.Pers. opastan “to fall,” patet “falls;” Av. pat- " to fly, fall, rush," patarəta- “winged;” cf. Skt. patati “he flies, falls,” pátra- “wing, feather, leaf;” Gk. piptein “to fall,” pterux “wing;” L. penna “feather, wing;” O.E. feðer “feather;” PIE base *pet- “to fly, rush”) + -â- interfix

• xiz present stem of xâstan, xizidan “to rise, get up” (Mid.Pers. xyz- “to stand up, rise;” Proto-Iranian *xiz- “to rise, ascend; increase”).

Continual rise and fall.

Etymology (EN): Verbal noun of → fluctuate.

Etymology (PE): Oftâxiz “fall and rise,” from oft “fall”
stem of oftâdan “to fall” (Mid.Pers. opastan “to fall,” patet “falls;” Av. pat- " to fly, fall, rush," patarəta- “winged;” cf. Skt. patati “he flies, falls,” pátra- “wing, feather, leaf;” Gk. piptein “to fall,” pterux “wing;” L. penna “feather, wing;” O.E. feðer “feather;” PIE base *pet- “to fly, rush”) + -â- interfix

• xiz present stem of xâstan, xizidan “to rise, get up” (Mid.Pers. xyz- “to stand up, rise;” Proto-Iranian *xiz- “to rise, ascend; increase”).

1. Light, downy particles, as of cotton.
   

2. A soft, light, downy mass (Dictionary.com).

Etymology (EN): Apparently a variant of floow “wooly substance, down, nap,” perhaps from Flemish vluwe, from Fr. velu “shaggy, hairy,” from L. vellus “fleece,” or L. villus “tuft of hair” (Online Etymology Dictionary).

Etymology (PE): Kork “down, soft wool, fluff,” of unknown etymology.

1. Light, downy particles, as of cotton.
   

2. A soft, light, downy mass (Dictionary.com).

Etymology (EN): Apparently a variant of floow “wooly substance, down, nap,” perhaps from Flemish vluwe, from Fr. velu “shaggy, hairy,” from L. vellus “fleece,” or L. villus “tuft of hair” (Online Etymology Dictionary).

Etymology (PE): Kork “down, soft wool, fluff,” of unknown etymology.

Of, resembling, or covered with fluff.

2. Light or airy (Dictionary.com).

Etymology (EN): From → fluff + -y adj. suffix, from O.E. -ig, cognate with L. -icus, → -ic.

Etymology (PE): Korkvâr “resembling fluff,” with -vâr, a suffix of possession, similarity, and aptitude (e.g., omidvâr, sezâvâr, sugvâr, šâhvâr, gušvâr), → -oid; korki adj. with -i.

Of, resembling, or covered with fluff.

2. Light or airy (Dictionary.com).

Etymology (EN): From → fluff + -y adj. suffix, from O.E. -ig, cognate with L. -icus, → -ic.

Etymology (PE): Korkvâr “resembling fluff,” with -vâr, a suffix of possession, similarity, and aptitude (e.g., omidvâr, sezâvâr, sugvâr, šâhvâr, gušvâr), → -oid; korki adj. with -i.

An aggregate of small particles loosely stuck together. Same as → porous dust grain.

See also: → fluffy; → dust; → grain.

An aggregate of small particles loosely stuck together. Same as → porous dust grain.

See also: → fluffy; → dust; → grain.

A continuous, amorphous substance whose molecules move freely past one another and that has the tendency to assume the shape of its container; collective term for liquids and gases.

Etymology (EN): From L. fluidus “fluid, flowing,” from fluere “to flow;” → flux.

Etymology (PE): Šârré, from šârr, → flux.

A continuous, amorphous substance whose molecules move freely past one another and that has the tendency to assume the shape of its container; collective term for liquids and gases.

Etymology (EN): From L. fluidus “fluid, flowing,” from fluere “to flow;” → flux.

Etymology (PE): Šârré, from šârr, → flux.

The branch of → fluid mechanics that deals with the movement of gases and liquids.

See also: → fluid; → dynamics.

The branch of → fluid mechanics that deals with the movement of gases and liquids.

See also: → fluid; → dynamics.

The branch of physics that extends the ideas developed in → mechanics and → thermodynamics to the study of motion and equilibrium of → fluids.

See also: → mechanics; → fluid.

The branch of physics that extends the ideas developed in → mechanics and → thermodynamics to the study of motion and equilibrium of → fluids.

See also: → mechanics; → fluid.

The ability of a substance to flow; reciprocal of → viscosity.

See also: → fluid + → -ity.

The ability of a substance to flow; reciprocal of → viscosity.

See also: → fluid + → -ity.

A type of → luminescence in which photons of lower energy are emitted as the result of absorption of energy by an atom or molecule from other radiation. The phenomenon lasts as long as the stimulus responsible for it is present.

See also: Coined by English mathematician and physicist Sir George G. Stokes (1819-1903) from fluor-, from → fluorspar, + → -escence, a suffix of nouns denoting action or process, change, state or condition, etc.

A type of → luminescence in which photons of lower energy are emitted as the result of absorption of energy by an atom or molecule from other radiation. The phenomenon lasts as long as the stimulus responsible for it is present.

See also: Coined by English mathematician and physicist Sir George G. Stokes (1819-1903) from fluor-, from → fluorspar, + → -escence, a suffix of nouns denoting action or process, change, state or condition, etc.

Possessing the property of → fluorescence.

See also: → fluorescence; → -escent.

Possessing the property of → fluorescence.

See also: → fluorescence; → -escent.

A tubular → electric discharge lamp in which light is produced by the → fluorescence → phosphors coating the inside of the tube.

See also: → fluorescent; → lamp.

A tubular → electric discharge lamp in which light is produced by the → fluorescence → phosphors coating the inside of the tube.

See also: → fluorescent; → lamp.

A compound (salt of hydrofluoric acid) containing → fluorine.

See also: → fluorine; → -id.

A compound (salt of hydrofluoric acid) containing → fluorine.

See also: → fluorine; → -id.

Gaseous chemical element; symbol F. It is the most reactive of all chemical elements. It is a yellowish, corrosive gas, which reacts with most organic and inorganic substances. → Atomic number 9; → atomic weight 18.9984; → melting point -219.62 °C; → boiling point -188.14 °C; → density 1.696 grams per liter at STP; → valence -1. Fluorine and its compounds are used in producing uranium (from the → hexafluoride) and more than 100 commercial fluorochemicals, including many high-temperature plastics.

See also: From L. fluere “flow, → flux,” since fluorspar (CaF₂) was used as a flux in metallurgy because of its low melting point. It was discovered in hydrofluoric acid by the Swedish pharmacist and chemist Carl-Wilhelm Scheele in 1771 but it was not isolated until 1886 by the French pharmacist and chemist Ferdinand Moisson.

Gaseous chemical element; symbol F. It is the most reactive of all chemical elements. It is a yellowish, corrosive gas, which reacts with most organic and inorganic substances. → Atomic number 9; → atomic weight 18.9984; → melting point -219.62 °C; → boiling point -188.14 °C; → density 1.696 grams per liter at STP; → valence -1. Fluorine and its compounds are used in producing uranium (from the → hexafluoride) and more than 100 commercial fluorochemicals, including many high-temperature plastics.

See also: From L. fluere “flow, → flux,” since fluorspar (CaF₂) was used as a flux in metallurgy because of its low melting point. It was discovered in hydrofluoric acid by the Swedish pharmacist and chemist Carl-Wilhelm Scheele in 1771 but it was not isolated until 1886 by the French pharmacist and chemist Ferdinand Moisson.

A → mineral composed of calcium fluoride, CaF₂, also called → fluorspar, that is often → fluorescent under → ultraviolet light.

See also: From fluor-, → fluorine, + → -ite.

A → mineral composed of calcium fluoride, CaF₂, also called → fluorspar, that is often → fluorescent under → ultraviolet light.

See also: From fluor-, → fluorine, + → -ite.

Same as → fluorite.

See also: From fluor-, → fluorine, + spar “a crystalline mineral.”

Same as → fluorite.

See also: From fluor-, → fluorine, + spar “a crystalline mineral.”

The amount of energy, fluid, or particles passing in a given direction in a unit of time.

Etymology (EN): O.Fr. flux, from L. fluxus, p.p. of fluere “to flow,” PIE base *bhleug- (cf. L. flumen “river;” Gk. phluein “to boil over, bubble up,” phlein “to abound”).

Etymology (PE): Šâr “outpouring of water, wine, etc.,” šâridan “to flow (as rivers), with a great noise; to pour,” âbšâr “waterfall;” saršâr “overflowing; brim-full;” Ossetic ægzælyn “to pour down;” Pashto zγâstəl/zγâl- “to swim;” Av. γžār- “to flow;” cf. Skt. ksar- “to flow;” Gk. phtheirein “to destroy, perish.”

The amount of energy, fluid, or particles passing in a given direction in a unit of time.

Etymology (EN): O.Fr. flux, from L. fluxus, p.p. of fluere “to flow,” PIE base *bhleug- (cf. L. flumen “river;” Gk. phluein “to boil over, bubble up,” phlein “to abound”).

Etymology (PE): Šâr “outpouring of water, wine, etc.,” šâridan “to flow (as rivers), with a great noise; to pour,” âbšâr “waterfall;” saršâr “overflowing; brim-full;” Ossetic ægzælyn “to pour down;” Pashto zγâstəl/zγâl- “to swim;” Av. γžār- “to flow;” cf. Skt. ksar- “to flow;” Gk. phtheirein “to destroy, perish.”

The → calibration of the flux received by a detector in terms of absolute units.

See also: → flux; → calibration.

The → calibration of the flux received by a detector in terms of absolute units.

See also: → flux; → calibration.

Flux of radiation that falls on a detector per unit surface area of the detector per unit bandwidth of the radiation per unit time.

See also: → flux; → density.

Flux of radiation that falls on a detector per unit surface area of the detector per unit bandwidth of the radiation per unit time.

See also: → flux; → density.

In radio astronomy, same as → jansky (symbol Jy), a unit of electromagnetic flux equivalent to 10^-26 watts per square meter per Hertz.

See also: → flux; → density.

In radio astronomy, same as → jansky (symbol Jy), a unit of electromagnetic flux equivalent to 10^-26 watts per square meter per Hertz.

See also: → flux; → density.

In Newton’s work on → calculus, the rate of change of a fluent (i.e. a flowing quantity), today commonly known as → variable. For a fluent x, the fluxion is denoted dx/dt. An obsolete mathematical term.

See also: From L. → fluxion-, stem of fluere “to flow,” → flux.

In Newton’s work on → calculus, the rate of change of a fluent (i.e. a flowing quantity), today commonly known as → variable. For a fluent x, the fluxion is denoted dx/dt. An obsolete mathematical term.

See also: From L. → fluxion-, stem of fluere “to flow,” → flux.

To move through the air using wings. Travel through the air or outer space.

Etymology (EN): M.E. flien, O.E. fleogan; cognate with O.H.G. fliogan, Ger. fliegen, O.Norse fljuga.

Etymology (PE): Infinitive from parvâz, → flight.

To move through the air using wings. Travel through the air or outer space.

Etymology (EN): M.E. flien, O.E. fleogan; cognate with O.H.G. fliogan, Ger. fliegen, O.Norse fljuga.

Etymology (PE): Infinitive from parvâz, → flight.

A trajectory that takes a → space probe close to a Solar System body (planet, satellite, asteroid, comet) but does not permit it to enter an orbit about the body.

Etymology (EN): → fly + by, from M.E., from O.E. be or bi, from P.Gmc. *bi “around, about” (cf. Du. bij, Ger. bei “by, at, near”), from *umbi, (cf. L. ambi “around, about,” Gk. amphi “around, about,” Skt. abhi “on both sides,”
Av. aibi, aiwi, O.Pers. aiby “to, against, in addition to,” Mid.Pers. aw-, ab-, Mod.Pers. af- (as in afzudan “to increase, add,” afruxtan “to inflame, kindle, blaze,” afqân “lamentation, groaning, cires for help”).

Etymology (PE): Barvâz, from bar- “on, up; upon, over,” → on-,

• vâz, as in parvâz, → flight.

A trajectory that takes a → space probe close to a Solar System body (planet, satellite, asteroid, comet) but does not permit it to enter an orbit about the body.

Etymology (EN): → fly + by, from M.E., from O.E. be or bi, from P.Gmc. *bi “around, about” (cf. Du. bij, Ger. bei “by, at, near”), from *umbi, (cf. L. ambi “around, about,” Gk. amphi “around, about,” Skt. abhi “on both sides,”
Av. aibi, aiwi, O.Pers. aiby “to, against, in addition to,” Mid.Pers. aw-, ab-, Mod.Pers. af- (as in afzudan “to increase, add,” afruxtan “to inflame, kindle, blaze,” afqân “lamentation, groaning, cires for help”).

Etymology (PE): Barvâz, from bar- “on, up; upon, over,” → on-,

• vâz, as in parvâz, → flight.