A distinguishable part of a sequence or cycle occurring over time. • That which is exhibited to the eye; the appearance which anything manifests, especially any one among different and varying appearances of the same object. • Any appearance or aspect of an object of mental apprehension or view. • A particular appearance or state in a regularly recurring cycle of changes with respect to quantity of illumination or form, or the absence, of a body's illuminated disk. Illustrated in Wikipedia's article Lunar phase. • Any one point or portion in a recurring series of changes, as in the changes of motion of one of the particles constituting a wave or vibration; one portion of a series of such changes, in distinction from a contrasted portion, as the portion on one side of a position of equilibrium, in contrast with that on the opposite side. • A component in a material system that is distinguished by chemical composition and/or physical state (solid, liquid or gas) and/or crystal structure. It is delineated from an adjoining phase by an abrupt change in one or more of those conditions. • In certain organisms, one of two or more colour variations characteristic of the species, but independent of the ordinary seasonal and sexual differences, and often also of age. • The period of play between consecutive breakdowns. • A haplotype. • The counterclockwise angle from the positive half of the real number line to the vector pointing to a complex number on an Argand diagram of the complex plane, which has the positive real line pointing right and the positive imaginary number line pointing up. • A distortion caused by a difference in the speed of propagation for different frequencies • In a polyphase electrical power system, one of the power-carrying conductors, or the alternating current carried by it.