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

1) General: An instance of changing, or something that changes.
2) Astro.: The periodic inequality in the Moon's motion that results from the combined gravitational attraction of the Earth and the Sun. Its period is half the synodic month, that is 14.77 days, and the maximum longitude displacement is 39'29''.9.
See also: → calculus of variations, → annual variation, → secular variation.

M.E., from O.Fr. variation, from L. variationem (nominative variatio) "difference, change," from variatus, p.p. of variare "to change," → vary.

Varteš, verbal noun from vartidan, → vary.

Of or describing a → variation.

→ variation; → -al.

Any of the physical principles that indicate in what way the actual motion of a state of a mechanical system differs from all of its kinematically possible motions or states. Variational principles that express this difference for the motion or state of a system in each given instant of time are called → differential. These principles are equally applicable to both → holonomic and → nonholonomic systems. Variational principles that establish the difference between the actual motion of a system during a finite time interval and all of its kinematically possible motions are said to be → integral. Integral variational principles are valid only for holonomic systems. The main differential variational principles are: the → virtual work principle and → d'Alembert's principle.

→ variational; → principle.

1) The quality or state of having different forms or types.
2) A number or collection of different things especially of a particular class.
3) Something differing from others of the same general kind.
4) Any of various groups of plants or animals ranking below a species (Merriam-Webster.com).

M.Fr. variété, from L. varietatem (nominative varietas) "difference, diversity; a kind, variety, species, sort," from varius, → various.

Vartiné, from vartin, → various, + noun/nuance suffix -é.

The → moment of the resultant of a → coplanar system of → concurrent forces about any center is equal to the algebraic sum of the moments of the component forces about that center.

Named after Pierre Varignon (1654-1722), a French mathematician, who outlined the fundamentals of statics in his book Projet d'une nouvelle mécanique (1687).

1) Of different kinds, as two or more things; differing one from another.
2) Marked by or exhibiting variety or diversity (Dictionary.com).

M.Fr. varieux and directly from L. varius "changing, different, diverse," → vary.

Vartin, from vart "change," present stem of vartidan, → vary, + adj. suffix -in.

1) To undergo change in form, substance, appearance, etc.
2) To change or alter. → covariance.

M.E. varien, from O.Fr. varier, from L. variare "change, alter, make different," from varius "variegated, different, spotted."

Vartidan "to change," from Mid.Pers. vartitan "to change, turn" (Mod.Pers. gardidan "to turn, to change"); Av. varət- "to turn, revolve;" cf. Skt. vrt- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wer- "to turn, bend."

Any physical quantity which requires a direction to be stated in order to define it completely, for example velocity. Compare with → scalar.

From L. vector "one who carries or conveys, carrier," from p.p. stem of vehere "carry, convey;" cognate with Pers. vâz (in parvâz "flight"); Av. vaz- "to draw, guide; bring; possess; fly; float," vazaiti "guides, leads" (cf. Skt. vah- "to carry, drive, convey," vahati "carries," pravaha- "bearing along, carrying," pravāha- "running water, stream, river;" O.E. wegan "to carry;" O.N. vegr; O.H.G. weg "way," wegan "to move," wagan "cart;" M.Du. wagen "wagon;" PIE base *wegh- "to drive").

Bordâr "carrier," agent noun from bordan "to carry, transport" (Mid.Pers. burdan; O.Pers./Av. bar- "to bear, carry," barəθre "to bear (infinitive);" Skt. bharati "he carries;" Gk. pherein "to carry;" L. ferre "to carry;" PIE base *bher- "to carry").

The study of → vectors and → vector spaces.

→ vector; → analysis.

Of a rotating body, a vector of magnitude ω (→ angular velocity) pointing in the direction of advance of a right-hand screw which is turned in the direction of rotation.

→ vector; → angular; → velocity.

In nuclear physics, a → boson with the spin quantum number equal to 1.

→ vector; → boson.

The study of vector functions between vector spaces by means of → differential and integral calculus.

→ vector; → calculus.

A → tensor density of → order 1.

→ vector; → density.

A vector each of whose → components is a → scalar field. For example, the → gradient of the scalar field F, expressed by: ∇F = (∂F/∂x)i + (∂F/∂y)j + (∂F/∂z)k.

→ vector; → field.

A function whose value at each point is n-dimensional, as compared to a scalar function, whose value is one-dimensional.

→ vector; → function.

Any particle of unit spin, such as the W boson, the photon, or the rho meson.

→ vector; → meson.

The perturbation in the → primordial Universe plasma caused by → vorticity. These perturbations cause → Doppler shifts that result in → quadrupole anisotropy.

→ vector; → perturbation.

Of two vectors, a vector whose direction is perpendicular to the plane containing the two initial vectors and whose magnitude is the product of the magnitudes of these vectors and the sine of the angle between them: A x B = C, C = |AB sin α|. The direction of C is given by the → right-hand screw rule. Same as → cross product. See also → scalar product.

→ vector; → product.

A system of mathematical objects consisting of a set of (muultidimensional) vectors associated with a set of (one-dimensional) scalars, such that vectors can be added together and vectors can be multiplied by scalars while preserving the ordinary arithmetic properties (associativity, commutativity, distributivity, and so forth).

→ vector; → space.

The brightest star in the constellation → Lyra and the 5th brightest star in the sky. It is an A type → main sequence star of visual magnitude 0.03. Vega is also one of the closer stars to the Earth, lying just 25.0 light-years away. Vega's axis of rotation is nearly pointing at the Earth, therefore it is viewed pole-on. Fast rotation has flattened Vega at its poles, turning it from a sphere into an oblate spheroid. The polar diameter of Vega is 2.26 times that of the Sun, and its equatorial diameter 2.75 solar. The poles are therefore hotter (10,150 K) than the equator (7,950 K).

Vega, from Ar. al-Waqi' contraction of an-Nasr al-Waqi' (النسر‌الواقع) "swooping eagle," from an-Nasr "eagle, vulture" + al-Waqi' "falling, swooping."