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

Large amplitude fluctuations in the → solar wind with properties resembling those of → Alfvén waves. A fluctuation is said to be Alfvénic if the following relationship between the velocity fluctuations (Δv) and magnetic field fluctuations (ΔB) is satisfied: Δv = ± ΔB/(μ₀ρ)^1/2. Also called Alfvénicity.

→ Alfvénic; → fluctuation.

→ Alfvénic fluctuation.

→ Alfvénic; → -ity.

→ Alfvénic fluctuation.

→ Alfvénic; → -ity.

A single-celled or multicellular plant living in water or moist conditions, which contain chlorophyll and other pigments but has no true root, stem, or leaf. Algae include seaweeds and pond scum.

From alga (singular), from L. alga "seaweed," of uncertain origin.

Jolbak "alga."

The branch of mathematics which deals with the properties and relations of numbers using symbols (usually letters of the alphabet) to represent numbers or members of a specified set; the generalization and extension of arithmetic.

Algebra, from M.L., from Ar. al jabr "reunion of broken bones," the first known use in the title of a book by the Persian mathematician and astronomer Abu Ja'far Mohammad ibn Musa al-Khwarizmi (c780-c850), who worked in Baghdad under the patronage of Caliph Al-Mamun. The full title of the tratise was Hisab al-Jabr w'al-Muqabala "Arithmetic of Completion and Balancing." → algorithm.

Jabr, from Ar. al jabr, as above.

Relating to, involving, or according to the laws of algebra.

→ algebra + → -ic.

An equation in the form of P = 0, where P is a → polynomial having a finite number of terms.

→ algebra; → equation.

A function expressed in terms of → polynomials and/or roots of polynomials. In other words, any function y = f(x) which satisfies an equation of the form P₀(x)yⁿ + P₁(x)y^{n - 1} + ... + P_n(x) = 0, where P₀(x), P₁(x), ..., P_n(x) are polynomials in x.

→ algebraic + → function.

A number, → real or → complex, that is a → root of a → non-zero polynomial equation whose → coefficients are all → rational. For example, the root x of the polynomial x² - 2x + 1 = 0 is an algebraic number, because the polynomial is non-zero and the coefficients are rational numbers. The imaginary number i is algebraic, because it is the solution to x² + 1 = 0.

→ algebraic; → number.

A star which lies at the lower left-hand corner of → Pegasus. Its apparent magnitude varies between +2.80 and +2.86 over a period of 3.6 hours; → spectral type B2 IV.

Algenib, from Ar. Aljanb al-Faras "the horse's flank," from al "the" + janb "flank" + faras "horse".

A binary system in Leo the brighter component of which (magnitude 2.6) is a giant K star and the partner a giant G (magnitude 3.8). The angular separation of just over 4'' means that the two stars are at least 170 AU apart, for a distance of 126 → light-years, and have an orbital period of over 500 years.

Algieba, from Ar. Al-Jabhah "the forehead" (of the Lion).

A variable star in the constellation → Perseus, which was the first eclipsing binary discovered. Its brightness varies between 2.2 and 3.5 magnitudes. Lying at a distance of about 82 → light-years, it consists of at least three components. The brightest component (A) is of spectral type B8 V, and the second one (B) a K type giant. The components A and B turn around each other with a period of about 68.8 hours.

Algol, from Ar. Ra's al-ghul "the ghoul's head".

The same as eclipsing binary stars, the prototype of which is Algol.

→ Algol; → variable.

1) A step-by-step problem-solving procedure, especially an established, recursive computational procedure for solving a problem in a finite number of steps.
2) Historically, the Arabic system of arithmetical notation (with the figures 1, 2, 3, etc.); the art of computation with the Arabic figures, one to nine, plus the zero; arithmetic.

From M.L. algorismus, a mangled transliteration of al-Khwarizmi, "native of Khwarazm," the surname of the Persian mathematician and astronomer Abu Ja'far Mohammad ibn Musa al-Khwarizmi (c780-c850).

Xârazmik, from Xârazmi (or Xwârazmi, from Xwârazm), the name of the Persian mathematician, + Persian affix → -ik, → -ics.

General:An assumed name; otherwise called.
Electronics: A false signal in telecommunication links from beats between signal frequency and sampling frequency.

From L. alius "(an)other". Compare with Skt. anya "other, different," Av. anya-, O.Pers. aniya- "the one or the other," Arm. ail, Gk. allos "another," Goth. aljis "other". PIE *al- "beyond".

Anyâ from Mid.Pers. anya "other, otherwise," from Av. anya "other". This term is used as eyni in the Modern Persian Aftari dialect: eyni sâl "other year," eyni vacé "other child".

The condition that two or more functions are indistinguishable because they have the same values at a finite set of points. Such functions are said to be aliases of each others. The aliasing problem often occurs in undersampled discrete Fourier transform.

Aliasing, from → alias + → -ing.

Anyâyi, from anyâ, → alias, + noun forming suffix -i.

A claim or piece of evidence that one was elsewhere when an act, typically a criminal one, is alleged to have taken place (OxfordDictionaries.com).

From L. alibi (adv.) "elsewhere, somewhere else," locative of alius "another, other, different," → alias.

Enigâh, literally "other place," from eni, from Mid.Pers. anya "other," → alias, +gâh "place," → time.

1) In a → planispheric astrolabe, the small revolving rod fixed to the center of the goniometric scale plotted on the → front or → back of the instrument. Unlike the → rule, the alidade has little vanes with holes or slots at each end, called → pinnules, which are used as sights, through which the observer can aim at a particular object. An index, often consisting of the edge of the alidade itself, shows on the goniometric scales the angle between the line of sight of the targeted object and a predetermined axis, i.e. the vertical of the observation locality (online museo galileo, VirtualMuseum).
2) A rule having a sight at each end, used in surveying.
3) A topographic surveying and mapping instrument used for determining directions, consisting of a telescope and attached parts.

M.E. allidatha, alhidade, from L. alhidada, from Ar. al-'izâda (العضاده), from al- "the" + 'izâda "an armlet, a bracelet; a sickle-like piece of metal, used by camel drivers, to pull down tree branches to camels."

Ezâdé, from Ar. al-'izâda.

1) A species not native to its environment; an introduced species.
2) A hypothetical creature from outer space; → extraterrestrial.

M.E., from O.Fr. alien "strange, foreign; a stranger, foreigner," from L. alienus "of or belonging to another, foreign, alien, strange," also, as a noun, "a stranger, foreigner," adjectival form of alius "(an)other," → alias; meaning "not of the Earth" first recorded 1920.

Bigâné "alien, foreigner," from Mid.Pers. bêgânag, from bêg-, bê- "out, outside, apart" (cf. Sogd. bêk "out, outside, apart, except," bêk-dênê "heretic," literally "out of religion") + suffix -ânag.

To arrange in a line or so as to be parallel; to adjust to produce a proper relationship or orientation.

M.Fr. aligner, from O.Fr. aligner, from à "to" + ligner "to line," from L. lineare, from linea "linen thread, string, line;" → line.

Âxatidan, from â- intesive and nuance prefix + xat, → line, + infinitive suffix -idan.