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

Forcible division into pieces of an object. → tidal disruption.

From L. disruptio "a breaking asunder," noun of action from p.p. stem of disrumpere "break apart, split, shatter, break to pieces," from → dis- "apart" + rumpere "to break."

Gosixt, past stem of gosixtan "to tear away, to beark off."

The act of dissecting.

→ dissect; → -tion.

The loss of energy over time by a → dynamical system, typically due to the action of → friction or → turbulence. The lost energy is converted into heat, raising the temperature of the system. See also: → Ohmic dissipation. → viscous dissipation.

Noun form of → dissipate.

General: An act or instance of dissociating; the state of being dissociated.
Chemistry: Separation of a molecule into two or more fragments (atoms, ions, radicals) by the absorption of electromagnetic radiation or the action of collisional phenomena.

From → dis- + (as)sociation, → association.

Energy required to dissociate a molecule. → dissociate.

→ dissociation; → energy.

A process where a positive molecular ion recombines with an electron, and as a result it dissociates into two neutral products. For example, AB⁺ + e^-→ A + B, where e^- is an electron, AB⁺ is a diatomic or polyatomic molecular ion, and A and B are the neutral fragmentation products. Dissociative recombination is the dominant recombination process in planetary ionospheres and interstellar clouds.

→ dissociative; → recombination.

Chemistry: The process by which a solid, gas, or liquid is dispersed homogeneously in a gas, solid, or a liquid.

Verbal noun of → dissolve.

Same as → metric.

→ distance + → function.

The distance separating an observer and the → apparent horizon of the place. Neglecting the → atmospheric refraction, it is given by: d = (2Rh)^1/2, where R is the radius of the Earth and h is the observer's height. This can be approximated to: d (km) = 3.57(h)^1/2 for a typical value of R = 6378 km. The atmospheric refraction, however, makes the thing more complex, depending on the temperature and density variations along the line of sight. Generally, refraction pushes the apparent horizon about 10% farther.

→ distance; → horizon.

1) The act or an instance of distinguishing or differentiating.
2) A distinguishing feature.
3) The state of being different or distinguishable.
4) Special honor, recognition, or fame (The FreeDictionary.com).

→ distinct; → -tion.

1) Extent to which a system, optical, acoustic, or electronic, fails to reproduce accurately at its output the characteristics of the input.
2) Optics: An optical imperfection caused by a → lens or → system of lenses which results in → magnification differences between different points on the → image. The points on the → object are misplaced in the image relative to the → center of the → field. See also → barrel distortion; → pincushion distortion.

Verbal noun of → distort.

An act or instance of distributing; the state or manner of being distributed; something that is distributed. → binomial distribution, → Bose-Einstein distribution, → brightness distribution, → chi-square distribution, → cumulative distribution function, → distribution function, → Gaussian distribution, → Gibbs canonical distribution, → lognormal distribution, → Maxwell-Boltzmann distribution, → normal distribution, → Poisson distribution, → power-law distribution, → probability distribution, → spectral energy distribution.

Verbal noun of → distribute

A function that gives the relative frequency with which the value of a statistical variable may be expected to lie within any specified interval. For example, the Maxwellian distribution of velocities gives the number of particles, in different velocity intervals, in a unit volume.

→ distribution; → function.

The aberration of a star's position due to the rotation of the Earth. Its value depends on the latitude of the observer, and is only 0''.32 in the case of an observer at the equator, where the rotational velocity is greatest.

→ diurnal; → aberration.

Daily geometrical libration of the Moon arising from the fact that observers at different points on the Earth see the Moon from slightly different angles. As the Moon rises in the east, you are positioned on one side of our planet, and by the time it sets in the west. Earth's rotation has carried you to the other side. This change in position produces a slight → parallax effect that adds about another 1° of libration in longitude. Two other geometrical libration are → libration in longitude and → libration in latitude. See also → physical libration.

→ diurnal; → libration.

The daily apparent motion of all celestial objects, due to Earth's rotation.

→ diurnal; → motion.

1) The act or process of dividing; state of being divided.
Math.: An operation in which a dividend is divided by a divisor to give a quotient and a remainder.
2) Something that marks a division; a separation.

From O.Fr. division, from L. divisionem (nom. divisio), from divid-, stem of dividere "to cleave, distribute," from → dis- "apart" + -videre "to separate," from PIE base *widh- "to separate."

1) Baxš "portion, part, division," baxšidan "to divide, distribute, grant;" Mod./Mid.Pers. baxt "fortune, fate," baxtan, baxšidan "to distribute, divide," bâq "garden," initially "piece or patch of land," baq "god, lord;" Av. bag- "to attribute, allot, distribute," baxš- "to apportion, divide, give to," baxta- "what is allotted (luck, fortune)," baxədra- "part, portion," baγa- "master, god;" O.Pers. bāji- "tribute, tax;" cf. Skt. bhaj- "to share, divide, distribute, apportion," bhájati "divides," bhakta- "allotted; occupied with; a share; food or a meal, time of eating?" pitu-bháj- "enjoying food;" Gk. phagein"to eat (to have a share of food)"; PIE base *bhag- "to share out, apportion."
2) Šekâf "a fissure, crack, slit," šekâftan "to divide into two long strips, split, break," Mid.Pers. škâftan.

A symbol placed between two quantities (dividend and the divisor) to indicate the division of the first by the second. The division sign is written as a horizontal line with dot above and dot below, ÷ (→ obelus), or a slash or horizontal line.

→ division; → sign.

1) The use of documentary evidence.
2) A furnishing with documents, as to substantiate a claim or the data in a book or article.
3) Computers: Manuals, listings, diagrams, and other hard- or soft-copy written and graphic materials that describe the use, operation, maintenance, or design of software or hardware (Dictionary.com).

→ document; → -tion.

A segment of the → zodiac extending 2.5 degrees, as considered in Babylonian and Hellenistic astrology; plural: dodekatemoria. Dodekatemoria result from a subdivision of each → zodiacal sign into twelve equal parts, each given the name of a → sign, beginning with the name of the sign being divided and continuing throughout the other eleven sequentially. Each zodiacal sign therefore contained a micro-zodiac within its own 30° span. Textual evidence for the micro-zodiac does not antedate the sixth century BC (F. Rochberg, 2010, In the Path of the Moon, BRILL).

From Gk. dodekatemorion "twelfth part," from dodekate "twelfth" (from dodeka "twelve") + morion "part."

Davâzdahân, from Mid.Pers. dwâzdahân "the twelve ones," from dwâzdah (Mod.Pers. davâzdah) "twelve;" Av. dvadasa, from dva "→ two" + dasa "→ ten."