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

A glass prism of very small angle used as an optical element to divert the path of a beam of light for a particular purpose. → absorbing wedge.

M.E. wegge; O.E. wecg "a wedge," cf. M.Du. wegge, Du. wig, O.H.G. weggi "wedge," Ger. Weck "wedge-shaped bread roll."

Gové "wedge;" Av. vada- "wedge," ^xvaδa- "deadly weapon;" cf. Skt. vadhá- "killer, deadly weapon," vadh- "to slay, kill;" Gk. othein "to push" (root of → osmosis).

A photometer in which an → absorbing wedge is inserted in the brighter of two beams until the flux densities of the two light sources are equal.

→ wedge; → photometer.

A division of time containing 7 successive days, which is completely independent of the month or the year. Unlike the month and the year, the week is an artificial unit of time, lacking an equivalent astronomical period.

M.E. weke; O.E. wice, cf. O.N. vika, M.Du. weke, O.H.G. wecha, Ger. Woche, akin to L. vicis "turn, change."

Hafté "week, hebdomad," from haft "seven" → hepta-.

If a function φ(x) is continuous on a closed interval [a,b], then for every ε > 0 there exists a polynomial P(x) such that |f(x) - P(x)| <ε, for every x in the interval.

After German mathematician Karl Wilhelm Theodor Weierstrass (1815-1897); → approximation; → theorem.

A test for uniform convergence of a sequence of functions. If there exists a series of numbers Σ M_i (summed from n = 1 to ∞), in which M_i≥ Σ |u_i(x)| for all x in the interval [a, b] and Σ M_i is convergent, the series u_i(x) will be uniformly convergent in that interval.

→ Weierstrass approximation theorem; M referring to → majorant; → test.

1) The force of attraction of the Earth on a given mass. → molecular weight; → weightlessness.
2) Statistics: A measure of the relative importance of an item in a statistical population. → weighted mean.
See also: → atomic weight, → counterweight, → mean molecular weight, → molecular weight, → statistical weight, → weight concentration, → weight fraction, → weight of a tensor density, → weight-fraction concentration, → weightlessness.

M.E., from O.E. gewiht, cf. O.N. vætt, O.Fris. wicht, M.Du. gewicht, Ger. Gewicht.

Vazn, loan from Ar. wazn.

of a gas included in the composition of a → gas mixture, the ratio of mass of this gas to the mass of the whole mixture. Same as → weight fraction and → weight-fraction concentration.

→ weight; → concentration.

Same as → weight concentration.

→ weight; → fraction.

A constant the value of which is characteristic for any given → tensor density.

→ weight; → tensor; → density.

Same as → weight concentration.

→ weight; → fraction; → concentration.

An mean which is obtained by combining different numbers according to the relative importance of each.

→ weight; → mean.

The phenomenon experienced by a body when there is no force of reaction on it. This happens when the body is in → free fall in a → gravitational field or when the net force on it is zero.

From → weight + -less suffix meaning "without" + -ness a suffix of quality or state.

Bivazni, from bi- "without," → a-, + vazn, → weight, + -i.

A → semiempirical → equation which describes the → binding energy of the → atomic nucleus. It is essentially a nuclear mass formula that provides the total binding energy per → nucleon as the sum of five terms:
E_b = a_VA - a_SA^2/3 - a_CZ²/A^1/3 - a_A(N -Z)²/A + δ(A,Z),
where the terms in the right-hand side of this equation are called the volume term, surface term, Coulomb term, asymmetry term, and pairing term, respectively. A, Z, and N are the number of nucleons, → protons, and → neutrons, respectively (see, e.g., Alexi M. Frolov, 2013, arxiv.org/pdf/1212.6768). Also called Bethe-Weizacker formula and → semiempirical binding energy formula.

Named after Carl Friedrich von Weizäcker (1912-2007), German physicist, who derived the formula in 1935, Z. für Physik 96, 431; → formula.

1) In a good or satisfactory manner; thoroughly, carefully, or soundly.
2) A hole drilled or bored into the earth to obtain water, petroleum, natural gas, brine, or sulfur (Dictionary.com).

1) M.E., from O.E. wel(l) (cognates Du. wel, Ger. wohl).
2) M.E. well(e), O.E. wylle, wella, welle (cognates: O.Saxon wallan, O.Fris. walla, O.H.G. wallan, Ger. wallen "to bubble, boil").

1) Xoš "good, well, sweet, fair, lovely," probably related to hu- "good, well," → eu-. Xub, ultimately from Av. huuāpah- "doing good work," → operate.
2) Câh "a well," from Mid.Pers. câh "a well;" Av. cāt- "a well," from kan- "to dig," uskən- "to dig out;" O.Pers. kan- "to dig," akaniya- "it was dug;" Mod.Pers. kandan "to dig;" cf. Skt. khan- "to dig," khanati "he digs," kha- "cavity, hollow, cave, aperture."

A string of → symbols from the alphabet of the → formal language that conforms to the grammar of the formal language. → closed wff, → open wff.

Wff, pronounced whiff; → well; → form; → formula.

A set in which every → nonempty → subset has a minimum element.

→ well; → order; → set.

A sequence of → permitted transitions in the → ultraviolet from an → excited state (C) of the → molecular hydrogen (H₂) to the electronic → ground state, with ΔE > 12.3 eV and λ ranging from 1160 Å to 1250 Å. When a hydrogen molecule absorbs such a photon, it undergoes a transition from the ground electronic state to the excited state (C). The following rapid → decay creates an → absorption band in that wavelength range. See also → Lyman band; → Lyman-Werner photon.

Named after the Danish physicist Sven Theodor Werner (1898-1984), who discovered the band (S. Werner, 1926, Proc. R. Soc. London Ser. A, 113, 107); → band.

The direction 90° to the left or 270° to the right of → north.

M.E., O.E. "west" "in or toward the west;" cf. O.N. vestr, O.Fris., M.Du., Du. west, Ger. West; PIE base *wes- (Gk. hesperos, L. vesper "evening, west").

Bâxtar "west;" Mid.Pers. apâxtar "north;" Av. apāxtar "northern."

Lying toward or situated in the west. → greatest western elongation.

Adjective from → west.

The position of a planet when it is visible in the eastern sky before dawn.

→ western; → elongation.