A chromatic scale consists of an ascending or descending sequence of 12 pitches, each a semitone or a half step apart.
The term chromatic derives from the Greek word chroma, which means color.
A chromatic scale can be played on the piano by using all black and white keys in order, without leaving any out.
The structure of a chromatic scale is therefore simple and uniform (all notes being separated by semitones), unlike major and minor scales which have tones and semitones in particular arrangements.
Study Op. 45, No. 16