CHROMATIC, a term meaning "coloured," used in science, particularly in the expression "chromatic aberration" or "disper sion" (see ABERRATION OF LIGHT). In Greek music ypwjcaruo µovauci was one of three divisions—diatonic, chromatic and enharmonic—of the tetrachord. Like the Latin color, Xpioµa was often used of ornaments and embellishments, and particularly of the modification of the three genera of the tetrachord. The chro matic, being subject to three such modifications, was regarded as particularly "coloured." To the Greeks chromatic music was sweet and plaintive. From a supposed resemblance to the notes of the chromatic tetrachord, the term is applied to a succession of notes outside the diatonic scale, and marked by accidentals. A "chromatic scale" is thus a series of semi-tones.