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

A birefrigent crystal, such as mica, that is characterized by having two optical axes along which light is propagated with equal velocities.

Biaxial, from → bi- "two" + axial, from → axe; → crystal.

A solidified substance in which the constituent atoms, ions, or molecules form a three-dimensionally periodic arrangement.

O.E. cristal "clear ice, clear mineral," from O.Fr. cristal, from L. crystallum "crystal, ice," from Gk. krystallos, from kryos "frost," from PIE base *kreus- "to begin to freeze, form a crust," → cryogenics.

Bolur, from Mid.Pers. bêlûr "crystal," Manichean Parthian bylwr, maybe of Indian origin, Pali veluriya- "a precious stone;" cf. Skt. vaidurya-, perhaps related to Tamil veliru, vilar "to become pale," or to the southern Indian city Velur, modern Belur. The Mid.Pers. word is perhaps the carrier between the Indian word and the Gk. beryllos, which has given rise to L. beryllus, O.Fr. beryl, E. beryl "the beryllium aluminum silicate, Be₃Al₂Si₆O₁₈."

The network of the points in space at which the atoms, molecules, or ions of a → crystal are regularly repeated.

→ crystal; → lattice.

The geometric framework to which a crystal may be referred and the arrangement of atoms or electron density distribution relative to that framework, usually determined by X-ray diffraction measurements.

→ crystal; → structure.

One of seven possible basic crystal types that is defined by the relations between the axis lengths and angles of its unit cell. Crystal systems can produce an infinite → lattice by successive translations in three-dimensional space so that each lattice point has an identical environment. The seven crystal systems are: → cubic, → orthorhombic, tetragonal, trigonal, hexagonal, monoclinic, and triclinic.

→ crystal; → system.

1) Of or like crystal; clear; transparent.
2) Formed by → crystallization.
3) Composed of crystals.
4) Pertaining to crystals or their formation (Dictionary.com).

Adjective from → crystal.

A → doubly convex, → transparent body in the → eye, situated behind the → iris, that focuses incident light on the → retina (Dictionary.com).

→ crystalline; → lens; → eye.

An arrangement and interrelationship of parts that is of → crystalline nature.

→ crystalline; → structure.

1) A state of molecular structure in some resins attributed to the existence of solid crystals with a definite geometric form.
2) The percentage of a polymer sample that has formed crystals (J. W. Gooch, Encyclopedic Dictionary of Polymers).

→ crystalline; → -ity.

A process by which a homogeneous solution becomes crystal.

Noun from crystallize, → crystal.

Noun from bolur, from verb boluridan "to crystallize" + verbal noun suffix -eš.

The science of forms, properties, and structure of crystals.

→ crystal; → -graphy; → -logy.

A → crystal system whose three axes have equal lengths and all corners are 90°.

→ cubic; → crystal; → system.

A → transparent → crystalline substance (such as calcite, quartz, and tourmaline) that is → anisotropic relative to the → speed of light. A ray incident normally on such crystals is broken up into two rays in traversing the crystal, → ordinary ray and → extraordinary ray.

→ doubly; → refracting; → crystal.

A tiny particle of ice within which → water molecules are all lined up in a precise → crystalline structure. Ice crystals come in various shapes including needles, → dendrites, hexagonal columns, and → platelet. If the temperature decreases the water molecules can crystallize, arranging themselves around the suspended impurities such as dust particles. See also → snow crystal.

→ ice; → crystal.

A type of material that possesses less geometrical regularity or order than normal solid crystals, and whose order varies in response to alterations in temperature, electric field, and other quantities.

→ liquid; → crystal.

A uniaxial, birefringent crystal in which the velocity of the extraordinary ray surpasses that of the ordinary ray.

→ negative; → crystal.

A → crystal system that has three mutually perpendicular axes, each of which is of a different length than the others.

→ orthorhombic; → crystal; → system.

A form of solid made up of ordered but non-repeating patterns of atoms, a symmetry that is forbidden for periodic crystals. In an ordinary crystal, only 1-, 2-, 3-, 4-, and 6-fold symmetries are possible, since these are the only symmetries that, when combined, can fill space. Prior to the discovery of quasicrystals, it was believed that 5-fold crystal symmetry could never occur. Quasicrystals are remarkable in that some of them display 5-fold or higher-fold forbidden symmetries. They are used as catalysts, in particular at high temperatures, to produce durable kinds of steel, like those used in objects such as razor blades and thin needles made specifically for eye surgery. The Nobel Prize in Chemistry 2011 was awarded to Daniel Schechtman for his discovery of quasicrystals in 1982.

→ quasi-; → crystal.

Pure natural crystalline form of → silica, SiO₂, which is transparent and colorless.

→ rock; → crystal.

An → ice crystal forming snow in a → cloud.

→ snow; → crystal.