In music theory, "diatonic" refers to a system of pitches or musical elements that belong to a specific key or scale. It encompasses the seven notes of a major or minor scale, along with the chords and harmonies derived from those notes within that key. Diatonic music adheres to the natural sequence of whole and half steps characteristic of the major or minor scale, without introducing chromatic alterations. This term is fundamental in understanding traditional tonal harmony and composition, as it forms the basis for most Western classical and popular music.