(chemistry, physics) A phase of matter similar to a liquid, in which the molecules are arranged regularly in one or two dimensions. / Material in that phase.

(optics) A doubly refracting crystal in which the index of refraction for the extraordinary ray is greater than for the ordinary ray, and the former is refracted nearer to the axis than the latter, such as quartz and ice; as opposed to negative crystal: one in which this characteristic is reversed, such as Iceland spar or tourmaline.

(crystallography) The intergrowth of two twin crystals.

a class of crystal consisting of a lattice of ions held together by their electrostatic interaction; they exhibit strong absorption of infrared radiation and have planes along which they cleave easily

(crystallography) either of two separate crystals that share crystal lattice points in a symmetrical manner and intergrow

(crystallography) A regular three-dimensional geometric arrangement of atoms, molecules or ions in a crystal

A material formed from by the growth of a crystal nucleus without secondary nucleation or impingement on other crystals; a regular three-dimensional structure extends throughout the material

(idiomatic) Completely clear and understood. / (idiomatic) Visually clear, a sharp image, high acuity.

A dye, derived from gentian violet, that is used as an acid-base indicator and as a biological stain.

A globe of glass or crystal used to foretell the future. / (by extension) A way of seeing into the future. / One of the magickal tools of Wicca, used for divination and altar purposes