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

Any large town or populous place.

M.E. cite, from O.Fr. cite "town, city," from L. civitas "citizenry; community," from civis "native, townsman;" related to L. cuna "cradle; bed;" Gk. kome "village;" Skt. śiva- "auspicious, dear;" O.E. ham "dwelling, house, village;" E. home; Ger. Heim (→ hamlet); Iranian dialects kiye "house, home;" Xonsâri ki "house;" Anâraki xiya, Tâti Karingân kâ, Sangesari keh "house, home;" PIE *kei- "to lie; bed."

Šahr "city," from Mid.Pers. šahr "land, country, city;" O.Pers. xša- "to rule," pati-xša- "to have lordship over," Xšyāršan- "hero among kings" or "ruling over heroes" the proper name of the Achaemenid emperor Helenized as Xerxes, upari.xšay- "to rule over," xšāyaθiya- "king;" Mid.Pers. šâh "king," pâdixšâ(y) "ruler; powerful; authoritative;" Mod.Pers. šâh "king," pâdšâh "protecting lord, emperor, monarch, king," šâyestan "to be worth, suit, fit;" Av. xšā(y)- "to rule, have power," xšayati "has power, rules," xšāyô "power;" cf. Skt. ksā- "to rule, have power," ksáyati "possesses;" Gk. ktaomai "I acquire," ktema "piece of property;" PIE base *tkeh- "to own, obtain."

A quantity that indicates a property of fluids and is defined by the ratio of shearing → stress to the rate of change of shearing → strain. It is also simply called viscosity. The coefficient of viscosity is expressed by: μ = (F/A) / (dv/dy), where F is the force required to maintain a steady velocity difference dv between any two parallel layers of the fluid, A is the area of the layers, and dv/dy is the → velocity gradient between two points separated by a small distance measured at right angles to the direction of flow. The unit of viscosity is that of force times distance divided by area times velocity. Thus, in the cgs system, the unit is 1 dyne.cm/cm².(cm/s), which reduces to 1 dyne.s/cm². This unit is called 1 → poise.

→ viscosity; → coefficient.

1) General: The quality of being coercive.
2) Physics: Same as → coercive force.

→ coercive; → -ity.

1) Collective character.
2) A collective whole.

→ collective; → -ity.

A mathematical property where all points lying on a line initially still lie on a line after transformation.

→ collinear; → -ity.

A form of → Hertzsprung-Russell diagram in which the luminosity is the vertical axis and the → color index the horizontal axis.

→ color; → luminosity, → diagram.

Density of the interstellar matter lying between an object and the Earth in a cylinder with a unity base.

→ column; → density.

The appearance of → gas and → dust features from the rocky-icy nucleus of a comet when approaching the Sun (→ cometary atmosphere, → cometary tail). The → sublimation of → water can explain cometary activity at distances from the Sun up to about 4 → astronomical units. At larger distances, the average temperature of the → comet nucleus' surface is less than 140 K, too low for efficient sublimation of water → ice. However, there are many examples of cometary activity at larger distances. This can probably be due to the sublimation of more → volatile → chemical species. Indeed, radio spectroscopic observations of comets at large distances have revealed an important → outgassing of → carbon monoxide (CO), which can sublimate at temperatures as low as 25 K.

→ cometary; → activity.

1a) A social group whose members share common characteristics or interests, such as values, identity, and often a common location (e.g. a village, town, or neighborhood).
1b) Ecology: A group of populations of different species (plants and animals) within a specified location in space and time. 2) Common ownership or participation; joint possession.

Ultimately from L. communitas "partnership, society, fellowship," from communis, → common "common, public, general," + -itas, → -ity

Hamdârgân, from hamdâr, → common, + -gân suffix forming plural entities, from Mid.Pers. -gânag, -gâna, on the model of hamegân, → public.

The state or quality of being commutative.

Noun from → commutative.

A population of relatively small (typically < 2°) → high-velocity clouds, which are spatially and kinematically isolated from the gas distribution in their environment. They are thought to be located in the → intergalactic medium of the → Local Group.

→ compact; → high-velocity cloud.

General: The fact or conditions of existing or working together.
Informatics: The ability of a software or peripheral device to function with another computer or computer system without modification.

Noun from → compatible.

The state or quality of being → complementary.

From → complementary + → -ity.

From osporandé, → complementary, + -gi, same as -i noun suffix.

Physical principle, put forward by Niels Bohr in 1928, that a complete knowledge of phenomena on atomic dimensions requires a description of both wave and particle properties.

→ complementarity; → principle.

The ability or quality to be reduced in volume. The coefficient of compressibility of a substance is given by c = (1/V).(δV/δp), where δV is the change in the volume resulting from a change of pressure δp, the temperature remaining constant.

Noun from → compressible.

Of an event B in relationship to an event A, the probability that event B occurs given that event A has already occurred. The notation for conditional probability is P(B|A), read as the probability of B given A: P(B|A) = P(A ∩ B)/P(A). → Bayes' theorem.

→ conditional; → probability.

1) General: A measure of the ability to transmit, as electricity, thermal energy, sound, and so on.
2) → electrical conductivity.
3) → thermal conductivity.

From → conductive + → -ity suffix forming abstract nouns expressing state or condition.

1) General: The state or ability of being connected.
2) Computers: The capacity of a machine to be connected to other facilities.

→ connective + → -ity.

A principle according to which the sum of probabilities of all possible states that might come out of an initial state equals the probability of the initial state.

→ conservation; → probability.

A → quantity that remains → constant when its corresponding → physical system undergoes a → transformation.

→ conserve→ quantity.