chromatic

Chromatic is an adjective derived from the Greek chroma, meaning color. It describes things related to color, color perception, or color systems, and it is contrasted with achromatic, meaning without color.

In color theory and vision, chromaticity distinguishes hue and saturation from luminance. Chromatic properties describe the hue of a color, while achromatic colors are grayscale. Chromaticity coordinates and diagrams express color independently of brightness.

In music, chromatic refers to the chromatic scale, a sequence of twelve pitches within an octave that includes all semitones. Chromatic harmony and chromaticism describe the use of semitone steps and non-diatonic notes beyond the standard major/minor scales.

In optics, chromatic aberration occurs when lenses bend different wavelengths of light by different amounts, causing color fringes. Optical designs may be achromatic or apochromatic to minimize this effect.

In mathematics, chromatic is used in graph coloring. The chromatic number of a graph is the smallest number of colors needed to color vertices so that adjacent vertices differ in color; the chromatic polynomial counts proper colorings as a function of the number of colors.

Other uses include contexts where color is a defining feature, such as describing colored substances or imaging signals. In chromatography, the term chromatic is sometimes used to describe color-based detection or visualization, though chromatography itself denotes separation by chemical properties rather than color.