An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The unit of → viscosity in the → cgs system, cm² s^-1, equal to 10^-4 m² s^-1.

After Sir George Gabriel Stokes (1819-1903), a British mathematician and physicist, who made important contributions to fluid dynamics, optics, and mathematical physics; → Stokes law; → Stokes parameter.

For the translational motion of a spherical body moving in a → viscous fluid, the proportionality factor between the uniform flow velocity far from the sphere and the drag force, provided no-slip boundary condition and small → Reynolds numbers: f = 6πηR, where η is the Reynolds number and R radius of the sphere.

→ Stokes; → friction; → factor.

1) Fluid mechanics: At low velocities, the frictional force on a spherical body moving through a fluid at constant velocity is equal to 6πRηv, where R is the radius of the sphere, η the fluid → viscosity, and v the velocity.
2) Spectroscopy: The wavelength of → luminescence excited by radiation is always greater than that of the exciting radiation.

→ Stokes; → law.

Four parameters which are needed to fully describe the → polarization state of → electromagnetic radiation. They involve the maximum and minimum intensity, the ellipticity, and the direction of polarization. The four Stokes parameters are traditionally defined as follows:
I ≡ total intensity.
Q ≡ I₀ - I₉₀ = difference in intensities between → horizontal and → vertical  → linearly polarized components.
U ≡ I₊₄₅ - I_-45 = difference in intensities between linearly polarized components oriented at +45° and -45° (or 135°).
V ≡ I_rcp - I_lcp = difference in intensities between right and left → circularly polarized polarized components.

→ Stokes; → parameter.

The hard nonmetallic mineral or group of consolidated minerals either in mass or in a fragment of pebble or larger size. See also → rock.

O.E. stan; cf. O.N. steinn, Dan. steen, O.H.G., Ger. Stein; from PIE *stai- "stone," also "to thicken, stiffen" (cf. Skt. styayate "curdles, becomes hard;" Av. stay- "heap;" Gk. stear "fat, tallow," stia, stion "pebble").

Sang "stone, rock;" Mid.Pers. sang; O.Pers. aθanga-; Av. asenga- "stone;" PIE *aken-.

A prehistoric period during which the main material used to make tools and weapons was stone. The Stone Age is usually divided into three separate periods (Paleolithic Period, Mesolithic Period, and Neolithic Period) based on the degree of sophistication in the fashioning and use of tools. The Paleolithic time period is by far the longest, beginning some two million years ago and ending around 10,000 BC to coincide with the end of the last ice age (Pleistocene epoch).

→ stone; → age.

A meteorite composed largely of rock-forming (→ silicate) → minerals. Stony meteorites are the most abundant kind, about 95%, of all meteorites. They are divided into two groups: → chondrites and → achondrites.

→ stone; → meteorite.

Meteorites comprised of roughly equal amounts of → nickel/→ iron and → stone. They are divided into two groups: → pallasites and → mesosiderites. The stony-irons are thought to have formed at the core/mantle boundary of their parent bodies. The stony-irons account for less than 2% of all known meteorites. Also called → siderolite.

→ stony; → iron; → meteorite.

1) To hinder or prevent the passage of. → stopping power.
2) The diaphragm used in optical instruments to cut off the marginal portions of a beam of light passing through lenses. → field stop; → stop number.

M.E. stoppen (v.), O.E. -stoppian (in forstoppian "to stop up, stifle"); V.L. *stuppare "to stop or stuff with tow or oakum" (cf. It. stoppare, Fr. étouper "to stop with tow"), from L. stuppa "coarse part of flax, tow."

1) Bâzdâštan, bâzdâšt- "to stop, restrain, inhibit, coerce, detain," from bâz-, → re-, + dâštan "to have, hold, maintain, possess," → access.
2) Daricé, literally "small door; window," from dar "door," + -cé diminutive suffix. Dar "door," Mid.Pers. dar, O.Pers. duvara-, Av. dvar-, cf. Skt. dvár-, Gk. thura, L. fores, P.Gmc. *dur-, O.E. duru, E. door, Lith. dvaras "court-yard;" PIE *dhwer-/*dhwor- "door, gate."

→ occlusive consonant.

→ stop; → consonant.

Same as → focal ratio.

→ stop; → ratio.

Vâbar, → ratio; kânuni, → focal.

A quantity indicating the extent with which a substance absorbs a → charged particle passing through it. It is the energy lost by a → non-relativistic particle per unit length of its path in the substance.

→ stop; → power.

Computers: A very commonly used word that is normally excluded by computer search engines. Stopwords have very little informational content, such as: and, the, of, it, as, may, that, a, an, of, off, etc.

→ stop; → word.

Rahâ-vâž, literally "free word," from rahâ "free, set free" (O.Pers. rad- "to leave," Skt. rah-, rahati "separates, leaves," Av. razah- "isolation;" PIE *redh-) + vâž, vâžé, → word. Fekan-vâž, literally "dropped word," from fekan present stem of fekandan, afkandan "to throw, cast away;" Mid.Pers. abgandan "to throw;" O.Pers. avakan- "to throw, place on," from Proto-Iranian *kan- "to throw, place, put."

An atmospheric disturbance with strong winds accompanied by rain, snow, or other precipitation and often by thunder and lightning.
A violent disturbance or upheaval.

M.E, from O.E. storm; cf. O.S., M.L.G., M.Du., Du. storm, O.H.G., Ger. sturm.

Tufân "storm; the roaring of the sea; noise, confused hum of men or animals," Lori tufo, Laki tuf "intense shower accompanied by wind," from tufidan "to roar, raise a tumult."

A narrative, either true or fictitious, in prose or verse, designed to interest, amuse, or instruct the hearer or reader; tale (Dictionary.com).

M.E. storie, from O.Fr. estorie, estoire "story, chronicle, history," from L.L. storia, shortened from L. historia "history, account, tale, story," → history.

Dâstân "story, fable, romance."

One who moves along slowly so as to remain some distance behind the person or people in front. → blue straggler.

From straggle "to wander from the proper path, to rove from one's companions," from M.E. straglen "to wander."

Veylân "wanderer, vagabond," of unknown origin, may be related to yalé "turned loose, vagabond, allowed to pasture at liberty, rover," or vel "set free."

Free from a bend, angle, or curve. → straight line.

M.E. streght, straight, from p.p. of strecchen, → stretch.

→ right.

A line without curvature or angles. A line whose → slope is → constant.

→ straight; → line.

Change of volume and/or shape of a body, or part of a body, due to an applied → stress. When a body is deformed by such a force, through compression or distension, the strain is the ratio of the dimensional change to the original or un-strained dimension. The strain may be a ratio of lengths, areas, or volumes. See also → shear.

M.E. streinen (v.), from O.Fr. estreindre "to bind tightly, clasp, squeeze," from L. stringere "to bind or draw tight," from PIE base *strenk- "tight, narrow; pull tight, twist;" cf. Gk. strangein "twist;" Lith. stregti "congeal;" O.H.G. strician "mends nets;" Ger. stramm, Du. stram "stiff."

Šepil "squeeze; fondness" (Dehxodâ) of unknown origin.

Unusual, not expected, extraordinary. → strange particle.

M.E., from O.Fr. estrange "foreign, alien," from L. extraneus "foreign, external," from extra "outside of," → extra-.

Šegeft, from Mid.Pers. škaft, škift, škuft "strange, wonderful, amazing;" Av. skapta- "wonderful."