A prefix meaning → six. → hexagon.
A prefix meaning "below," used with second elements of any origin. → infrared; → infrasound.
From L. infra "below, underneath, beneath," from PIE *ndher; cf. Mod.Pers. zir "below, down," akin to → under-.
Foru-, from foru "down, downward; below; under, beneath; low," from Mid.Pers. frôt "down, downward;" O.Pers. fravata "forward, downward;" cf. Skt. pravát- "a sloping path, the slope of a mountain."
darun- (#), dar- (#); foru- (#)
Prefix denoting: "inside, within; below." → intramolecular forces; → intermolecular forces; → intramercurian planet.
From L. intra "on the inside, within; during; below." Commonly opposed to → extra-.
Darun "in, into; within" (Mid.Pers. andarôn
"inside," from andar, → inter-, + rôn
"side, direction;" Av. ravan- "(course of a) river").
1) Prefix, often meaning "large, great."
From Gk. megas "great, large, mighty," from PIE *meg- "great;" cf. L. magnus, Goth. mikils, O.E. micel.
A prefix appearing in loanwords from Gk., with the meanings 1) "after, behind;" 2) "changed, altered;" 3) "higher, beyond." → metagalaxy; metaphysics; → metastable.
From Gk. meta (prepositin) "in the midst of, among, with, after," originally me-ta (Mycenaean Greek), from PIE *me- "in the middle" (cf. Goth. miþ, O.E. mið "with, together with, among," E. with).
Matâ-, from Av. matay-, mati- "protrusion of mountain range," framanyente "to be protruding, jutting;" from PIE base *men- "to stand out, to project;" cf. L. mons (genitive montis) "mountain," minere "to project, jut, threaten" (other related terms: mouth, prominent, amount, etc.).
hašt-, octa-, oct-
Fr.: octa-, octo-, oct-
A prefix meaning eight.
From L. octo, Gk. okto, cognate with Pers. hašt, as below. Skt. asta, Goth. ahtau, O.E. eahta (see eight).
Hašt "eight," from Mid.Pers. hašt, O.Pers.*aštahva-
"eighth;" Av. ašta; cf. Skt. astā;
Ossetic ast; (Buddhist) Sogdian 'št;
Gk. okto, L. octo
(Fr. huit; Sp. ocho);
P.Gmc. *akhto(u) (O.E. eahta, æhta, E. eight,
O.N. atta, Ger. acht, Goth. ahtau); PIE base *oktô(u).
pârâ- (#), parâ- (#)
1) A prefix occurring in loanwords from Gk. with the meanings
"beside, alongside of, by, beyond."
From Gk. para-, from para (preposition) "beside, near, from, against, contrary to," cognate with Av. parā, as below; L. pro "before, for, in favor of," per- "through;" Goth. faur "along;" O.E. for- "off, away."
Pârâ-, parâ-, from O.Pers. parā (adv.) "along; forth;" Av. parā (adv.) "at first, in the first place; in former times, formerly;" also "away, aside;" cf. Skt. purā: "before, formerly;" cognate with Gk. para, as above.
Fr.: eau para
The → water molecule in which the → nuclear spins of the constituent → hydrogen atoms are → antiparallel (→ parahydrogen). See also: → ortho-water.
Prefix denoting five, fivefold (e.g. pentacyclic, pentahedron, pentahydrate).
From Gk. pent-, penta-, combining forms from pente "five;" cognate with Pers. panj, E. five, as below.
Panj, from Mid.Pers. panj, Av. panca; cf. Skt. pánca; Gk. pente; L. quinque; O.E. fif, from P.Gmc. *fimfe (O.S. fif, O.H.G. funf); from PIE base *penkwe "five."
A prefix denoting 1015.
Of unknown origin.
soft gamma-ray repeater (SGR)
bâzgaršgar-e partowhâ-ye gâmmâ-ye narm
Fr.: répéteur des rayons gamma mous
Same as → soft gamma repeater (SGR).
farâz, bâlâ, abar-
A prefix denoting "over, above, beyond, greater than."
From L. supra "above, over, before, beyond," → super-.
Farâz "above, up, upon," → height; bâlâ "above, up, high," → height; abar-, → super-.
Fr.: couche super-eddingtonienne
In some stellar models, particularly for evolved → massive stars, such as → red supergiants, → Luminous Blue Variables, and → Wolf-Rayet stars, an outermost layer of the stellar envelope where the luminosity might exceed the → Eddington limit. This is due to the → opacity peak produced by the variation in the ionization level of hydrogen in the outer → convective envelope, beneath the surface, of very luminous stars. The opacity peak generates supra-Eddington layers and density inversion. The high opacity decreases the Eddington luminosity in these layers, possibly to fainter levels than the actual stellar luminosity. As a result, the → radiative acceleration exceeds the → gravitational acceleration leading to → mass loss enhancement (see, e.g., A. Maeder, Physics, Formation and Evolution of Rotating Stars, Springer, 2009).
→ supra-; → Eddington limit; → layer.
supra-horizontal branch star
setâre-ye farâz-e šâxe-ye ofoqi
Fr.: étoile au-dessus de la branche horizontale
A member of a rare class of objects found in → globular clusters to lie about one magnitude above and to the blue part of the → horizontal branch. These stars are identified as post → EHB stars on their way from to the → asymptotic giant branch.
→ supra-; → horizontal; → branch; → star.
Prefix denoting one million million (1012).
From Gk. teras "monster."
Combining form meaning four.
From Gk. tetra-, combining form of tettares, tessares "four," cognate with Pers. cahâr, → four.
A prefix occurring originally in loanwords from L., with the basic meaning "on the far side of, beyond, extremely."
From L. ultra- from ultra (adverb and preposition) "beyond, on the further side," from *ulter, from uls "beyond;" + *-ter suffix of comparative adj.; PIE base *al- "besides, other, beyond."
Ultar-, from Mid.Pers. ul "up, upward," ulêh "upward, above" (Av. ərəδuua- "upright, risen; cf. Skt. ūrdhvá- "high, above, elevated; Gr. orthos "set upright, straight;" L. arduus "high, steep;" → ortho-) + -tar suffix forming comparative adjectives (Mid.Pers. -tar; Av. -tara- (masculine); PIE base *-tero).
ultra-diffuse galaxy (UDG)
Fr.: galaxie ultra-diffuse
A galaxy of low stellar density, defined to have low central → surface brightness (> 24 mag arcsec-2) and an → effective radius (Re) of over 1.5 kpc. The question of whether UDGs represent a separate class of galaxies is still under debate. Currently, known UDGs that have been discovered in clusters, in groups, and in the field can have Re as large as 5 kpc which is comparable to that of giant Milky Way like galaxies. This fact has been used to suggest that UDGs are "failed" giants. As Re captures (at most) the central parts of giant galaxies, whether this radius can be used to fairly compare the sizes of UDGs to the more massive galaxies is questionable (see, e.g., Chamba et al., 2020, A&A 633, L3).
Term proposed by van Dokkum et al. (2015), arXiv: 1410.8141v2; → ultra-; → diffuse; → galaxy.
ultra-high-energy cosmic ray (UHECR)
partowhâ-ye keyhâni-ye ultar-meh-kâruž
Fr.: rayons cosmiques de très haute énergie
A particle belonging to the most energetic population of → cosmic rays with an energy above ~ 1020 → electron-volts. The UHECRs constitute a real challenge for theoretical models, because their acceleration requires extreme conditions hardly fulfilled by known astrophysical objects. See also → UHECR puzzle, → Greisen-Zatsepin-Kuzmin cutoff.
→ ultra- + → high-energy cosmic ray.
Fr.: neutrino ultra haute énergie
A neutrino particle accelerated to energies above 1018 → electron-volts. They are produced by the interaction of → ultra-high-energy cosmic ray (UHECR)s with the → cosmic microwave background radiation. Also called → cosmogenic neutrinos. See also → Greisen-Zatsepin-Kuzmin limit.