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

To grow or increase gradually, by the process of → accretion.

Back-formation from → accretion.

The gas involved in various accretion processes, such as that fed into an → accretion disk, pulled by a compact object, or used in the mass growth of a galaxy.

→ accretion; → gas.

1a) Relating to a particular instance or object, as opposed to → general.
1b) Relating to or characteristic of things capable of being perceived by the senses, as opposed to → abstractions.
1c) Formed by the coalescence of particles; condensed; solid.
2a) To form into a mass by coalescence of particles; render solid. → concretion.
2b) To make real, tangible, or particular.

M.E. concret, from L. concretus "condensed, hardened, thick, stiff, clotted," p.p. of concrescere "to grow together," from → com- "together" + crescere "to grow," cognate with Pers. korré "foal, colt," korr "son, boy," → crescent.

Ambas, a variant of anbast in several dialects (e.g. Tabari) "dense, thick;" Mid.Pers. hambast "compact, tied together," from ham- "together," → com- + bast p.p. of bastan "to clot, congeal; to bind," Av./O.Pers. band- "to bind, fetter," basta- "bound, tied," Skt. bandh- "to bind, tie, fasten," PIE *bhendh- "to bind," cf. Ger. binden, E. bind.
Basudani "tangible," from basudan "to touch," variant pasâvidan, ultimately from Proto-Ir. *pra-sau-, from *sau- "to rub; whet; wear;" cf. sudan, sâyidan "to rub," sân "whetstone," variants fasân, afsân, awsân; Mid.Pers. sūdan "to rub;" Khotanese sauy- "to rub;" Sogd. ps'w "to rub;" Choresmian bs'w "to rub off, polish;" Skt. sā- "to sharpen, whet."

Apart or detached from others; separate; distinct. Composed of distinct or discontinuous elements.

From O.Fr. discret, from L. discretus "separated, distinct," from p.p. of discernere "to distinguish," from → dis- "off, away" + cernere "distinguish, separate, sift," → crisis.

Gosasté "broken, broken off," p.p. of gosastan "to break, split," Mid.Pers. wisistan "to break, split," Av. saed- "to split," asista- "unsplit, unharmed," Skt. chid- "to split, break, cut off," Gk. skhizein "to split," L. scindere "to split;" PIE stem *skei- "to split, cut."
Jodâ "separate, distinct," Mid.Pers. jutâk (yutâk), jut (yut).

The rapid, systematic changes in the absorption parts of the → P Cygni profiles of the ultraviolet → resonance lines (Si IV, C IV, and N V) observed in a majority of massive → hot stars. DACs are typically seen to accelerate to the → blue wing of the profile over a few days, becoming narrower as they approach the → terminal velocity.

→ discrete; → absorption; → component.

Data that can only take a small set of particular values, usually whole numbers. For instance, number of children in a family cannot be 2.4, since parents cannot actually have 2.4 children. → continuous data.

→ discrete; → data.

A localized source on the celestial sphere that can be observationally separated at radio wavelengths from its background emission.

→ discrete; → radio; → source.

A spectrum in which the component wavelengths (and wave numbers and frequencies) constitute a discrete sequence of values (finite or infinite in number) rather than a continuum of values.

→ discrete; → spectrum.

A transition between two quantum-mechanical energy levels. See also → discrete spectrum.

→ discrete; → transition.

A quantity that has certain magnitudes and does not represent a → continuous variable.

→ discrete; → value.

A variable which has only → discrete values and has no in-between values.

→ discrete; → variable.

A → quantum walk involving a probabilistic → operator that changes the direction while leaving the position fixed, and a shift operator that changes the position. Discrete-time quantum walk was introduced by J. Watrous (2001, Journal of Computer and System Sciences 62, 376)

→ discrete; → time; → quantum; → walk.

The component of a → planispheric astrolabe that is held against the → tympanum by the → horse, but can rotate freely in the → mater around the → pin to simulate the daily movement of the stars in the sky. It is the most characteristic part of the planispheric astrolabe.

From L. rete "net."

Tanandu "spider," from tanidan "to spin," → tension; ankabut "spider," loan from Arab.