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

The complement of → declination; the angular distance along a great circle from the celestial pole, i.e., 90° - declination.

Codeclination, from → co- + → declination.

Hamvâkil, from ham-, → co-, + vâkil, → declination.

The set of values that a → function is allowed to take (i.e. may possibly come out of a function), as opposed to the → range.

→ co-; → domain.

1) Math.: A number or letter placed before an algebraic expression to indicate that the expression is to be multiplied by that factor, e.g. in the expression 2 x³, 2 is the coefficient of x³. In general, any factor of a product is called the coefficient of the product of the remaining factors.
2) Physics: Factor which measures some specified property of a given substance, and is constant for that substance under given conditions, such as the coefficient of friction. → factor.

Hamgar, from ham- "together," → com- + -gar agent suffix, from kar-, kardan "to do, to make," 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."

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.

A flat mirror with a clock-drive mounted in such a way that it moves from east to west to compensate for the apparent rotation of the Earth in order that the image of a particular area of sky remains fixed in the focal plane. See also → siderostat and → heliostat.

Coelostat, from L. coelo-, for caeli-, combination form of coelum "sky" + -stat prefix denoting something that stabilizes, keeps, fixes, from -stata, from Gk. -states "one that causes to stand," or statos "standing," from *sta- "to stand."

Âsmândâštâr, from âsmân, → sky, + dâštâr "holder, maintainer," from dâštan "to hold, maintain; to have; to possess," Mid.Pers. dâštan, O.Pers./Av. root dar- "to hold, keep back, maitain, keep in mind," Skt. dhr-, dharma- "law," Gk. thronos "elevated seat, throne," L. firmus "firm, stable," Lith. daryti "to make," PIE *dher- "to hold, support."

1) To compel by force, especially by law or authority.
2) To obtain through the use of force, threat, or other forms of constraint.

M.E., from O.Fr. cohercier, from L. coercere "to restrain, surround," form → com- "together" + arcere "to enclose, confine, keep off," from PIE *ark- "to hold, contain, guard."

Pazuridan, literally "to force against," from pa- "contrary to; against; opposing," → counter- + zur "power, force," → strength, + infinitive suffix -idan.

The act, practice, or power of using physical or moral force to compel a person to do something.

Verbal noun of → coerce.

Serving or tending to coerce.

→ coerce; → -ive.

Same as → coercive force.

→ coercive; → field.

The strength of an external → magnetic field that brings to zero the → magnetic flux density of a magnetic material when that field is caused to operate in the opposite direction from the orientation of the → magnetization of the material. Also called coercivity. Coercive force is a measure of the magnetization of a → ferromagnetic material. It is usually measured in the units of → oersted or ampere/m.

→ coercive; → force.

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

→ coercive; → -ity.

Of the same age.

From L. co-, → com-, + aevum "age," → aeon.

Hamsenn "equally old," from ham-, → com-, + senn→ age.

A number associated with an → element of a → determinant. If A is a square matrix [a_ij], the cofactor of the element a_ij is equal to (-1)^i+j times the determinant of the matrix obtained by deleting the i-th row and j-th column of A.

→ co-; → factor.

1) The mental process of knowing, including → awareness, → perception, → reasoning, and judgment.
2) The product of such a process; something thus known, perceived, etc. (Dictionary.com).

M.E. cognicioun; L. cognitionem (nominative cognitio, from cognitus p.p. of cognoscere, from → co- + gnoscere, noscere "to learn;" cognate with Pers. šenâs, šenâxt, as below.

Šenâxtâr, verbal noun of šenâxtan "to know, recognize," dânestan "to know;" O.Pers./Av. xšnā- "to know, learn, come to know, recognize;" cf. Skt. jñā- "to recognize, know," jānāti "he knows;" Gk. gignoskein "to know, think, judge;" L. gnoscere, noscere "to come to know" (Fr. connaître; Sp. conocer); O.E. cnawan; E. know; Rus. znat "to know;" PIE base *gno- "to know."

1) Of or pertaining to the act or process of knowing, perceiving, remembering, etc.; of or relating to → cognition.
2) Of or pertaining to the mental processes of perception, memory, judgment, and reasoning, as contrasted with emotional and volitional processes (Dictionary.com).

→ cognition; → -ive.

1) To stick together; be united; hold fast, as parts of the same mass.
2) Physics (of two or more similar substances) to be united within a body by the action of molecular forces (→ cohesion).

From L. cohaerere "to cleave together," from → com- "together," + haerere "to stick."

Hamdusidan, from ham- "together," → com-, + dusidan (Dehxodâ) "to stick, to adhere," → adhere.

The property of two or more electromagnetic waves when they are in fixed phase relationship over time. If the crests and troughs of the waves meet at the same time and place they are said to be in phase.

→ cohere + -ence, → -ance.

Of an electromagnetic wave, the area of a surface perpendicular to the direction of propagation, over which the electromagnetic wave maintains a specified degree of coherence.

→ coherence; → area.

The distance over which an electromagnetic wave train maintains a specified degree of coherence.

→ coherence; → length.

The time over which a propagating electromagnetic wave may be considered coherent. The coherence time of an interferometer is the interval during which the fringe phase remains stable.

→ coherence; → time.