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

A change in the → energy level or → state of an → atom in which a → quantum of energy is either gained or lost. See also → forbidden transition; → permitted transition; → semiforbidden transition.

→ atomic; → transition.

The volume one → mole of a → chemical element occupies at room temperature. Atomic volume is typically given in cubic centimeters per mole (cc/mol). In other words, atomic volume is the ratio of → atomic mass to the → density of an element.

→ atomic; → volume. .

A graph displaying → atomic volumes of → chemical elements against their → atomic masses, first plotted by Lother Meyer (1830-1895). The elements with similar properties occupy the same positions on the graph. In the original curve, Lothar Meyer plotted atomic volumes against → atomic weights. → Alkali metals such as Na, K, Rb, and Cs occupy the top position on the graph. Elements like Be, Mg, Ca, Sr, and Ba occupy the positions on the ascending part of the graph. → Inert gases, except He, occupy the positions on the descending part of the graph. → Halogen elements like F, Cl, and Br also occupy the descending part of the graph.

→ atomic; → volume; → curve.

→ relative atomic mass.

→ atomic; → weight.

i) If t₁, t₂, ..., t_n are terms and P is a → predicate of arity n, then P(t₁, t₂, ..., t_n) is an atomic wff.
ii) If t₁ and t₂ are terms, then (t₁ = t₂) is an atomic wff.

→ atomic; → wff.

1a) An aggressive and violent act against a person or place.
1b) Chem.: The beginning of a series of destructive reactions.
2a) To apply aggressive military action against (a place or enemy forces).
2b) Chem.: To begin a destructive reaction by breaking a bond or forming a new bond.

From M.Fr. attaquer, from Florentine Italian attaccare (battaglia) "join (battle)."

Patâk, from pa-, short for pati- "contrary, opposite" (az in panâh, padid), → against, + tâk, variants tak, tag, tâz "rush, running, attack," related to tâxtan "to run; to hasten; to assault," → flow.

1) To pay attention.
2) To be present at.

M.E. atenden, from O.Fr. atendre "to expect, wait for, pay attention," from L. attendere "give heed to," literally "to stretch toward," from → ad- "to" + tendere "stretch," → tension.

Âtânidan, from prefix â- + tân, from tan-, tanidan "to spin, twist, weave" (cf. tân "thread, warp of a web," variants târ "thread, warp, string," tâl "thread" (Borujerdi dialect), tur "fishing net, net, snare"); Mid.Pers. tanitan; Av. tan- to stretch, extend;" cf. Skt. tan- to stretch, extend;" tanoti "stretches," tantram "loom;" tántra- "warp; essence, main point;" Gk. teinein "to stretch, pull tight;" L. tendere "to stretch;" Lith. tiñklas "net, fishing net, snare;" PIE base *ten- "to stretch."

1) The act or state of attending.
2) The act or state of going to or being present at a place or event.
3) The persons or number of persons present at a particular place or event.

→ attend; → -ance.

A person who is present at a specific time or place.

From → attend + suffix -ee

Âtângar agent noun from → attend; pârgertandé agent noun from pârgertidan, → participate.

1) The act or faculty of attending, especially by directing the mind to an object.
2) Observant care; consideration (Dictionary.com).

→ attend; → -tion.

1) Characterized by or giving attention; observant.
2) Thoughtful of others; considerate; polite; courteous (Dictionary.com).

→ attend; → -ive.

1) To reduce in force, value, amount, or degree. → attenuation, → attenuation factor.
2) To reduce the amplitude of an electrical signal with little or no distortion.

L. attenuatus, p.p. of attenuare "to make thin," from → ad- "to" + tenuare "make thin," from tenuis "thin;" cf. Gk. tanaos "thin, slender, elongated;" Skt. tanuka-, tanu- "thin;" Av. tan- "to stretch;" Pers. tonok "thin," as below; O.Ir. tanae "delicate, thin;" O.H.G. dunni "thin."

Tonokidan, from tonok "thin, slender, slight, tender, delicate" + -idan, infinitive suffix. Tonok, from Mid.Pers. tanuk, Av. root tan- "to stretch, extend," cognate with L. tenuis, as above.

The falling off of the energy density of radiation with distance from the source, or with passage through an absorbing or scattering medium.

Verbal noun of → attenuate.

The fraction of a beam of → X-rays or → gamma rays that is absorbed or scattered per unit thickness of the → absorber. The linear attenuation coefficient, denoted by the symbol μ, appears in the equation I(x) = I₀e^-μx, where I(x) is the intensity at depth of x cm and I₀ is the original intensity.

→ attenuation; → coefficient.

The ratio of the radiation intensity after traversing a layer of matter to its intensity before.

→ attenuation; → factor.

Position of a satellite with respect to the horizon or some other fixed reference plane.

Fr., from It. attitudine "disposition, posture," from L.L. aptitudo "faculty."

Ruykard, noun from ruy kardan "to turn the face toward," from ruy "face" (Mid.Pers. rôy, rôdh "face," Av. raoδa- "growth," in plural "appearance," from raod- "to grow, sprout, shoot," cf. Skt. róha- "rising, height") + kardan "to do, make, perform" (Mid.Pers. kardan, O.Pers./Av. kar- "to do, make, build," Av. kərənaoiti "makes," cf. Skt. kr- "to do, to make," krnoti "makes," karma "act, deed;" PIE base k^wer- "to do, to make").

→ position.

A prefix meaning 10^-18.

From Danish or Norwegian atten "eighteen," from O.N. attjan "eighteen," from atta "eight" (compare with Gk. okto, L. octo, Skt. astau, Av. ašta-, Mod.Pers. hašt; PIE *okt(u)) + tjan "ten" (compare with Skt. dasa, Av. dasa, Mod.Pers. dah, Gk. deka, L. decem; PIE *dekm).

To cause to draw near or adhere by physical force.

L. attractus, p.p. of attrahere "to draw, to attract," from ad- "to" + trahere "to pull, draw."

Darkašidan, from dar- "in, into" + kašidan "to draw, attract," → galaxy.

The act or capability of attracting. A physical force (gravitational, electric, magnetic, etc.) exerted by material bodies.

Attraction, n. from → attract.

Having the quality of attracting.

Verbal adj. from → attract.