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

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 wave maintains a specified → degree of coherence. According to the van Cittert-Zernike theorem, the coherence area is given by: A_c = D²λ²/(πd²), where d is the diameter of the light source and D is the distance away. The coherence area is an important parameter in photon correlation experiments. In the → Young's experiment the → interference pattern is only seen if slits are inside one coherence area.

→ coherence; → area.

The distance over which an → electromagnetic wave train maintains a specified → degree of coherence. The coherence length is related to the → coherence time multiplied by vacuum → velocity of light.

→ 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.

Two or more wave sources are said to be coherent sources if the phase difference between a pair of points, one in each source, remains constant.

Coherent, adj., → coherence.

Light waves that have the same wavelength and possess a fixed phase relationship, as in a laser.

→ coherent; → light.

A branch of optics that uses coherent radiation to produce holographic three-dimensional images of objects.

→ coherent; → optics.

A scattering process in which the scattered radiation bears the same frequency and phase as the incident radiation.

→ coherent; → scattering.

One of two light beams derived from the same source in → interference experiments. It is impossible to obtain interference from two separate sources because their → wavefronts do not have a constant → phase difference. In → Young's experiment, → Fresnel's biprism, → Fresnel's mirrors, and → Lloyd's mirror the two sources always have a point-to-point correspondence of phase, since they are both derived from the same source.

→ coherent; → source.

Holding together.
Physics: The attraction between the molecules of a solid or liquid that holds the parts of the substance together.

From L. cohæsus, p.p. of cohærere "to stick together," → coherence.

Hamduseš, verbal noun from hamdusidan "to cohere," → coherence.

1) Of or pertaining to the molecular force → cohesion.
2) Characterized by or causing → cohesion.

Adjective from → cohere.