Diatonic function

In tonal music theory, a diatonic function (also chord area) is the specific, recognized role of each of the 7 notes and their chords in relation to the diatonic key. In this context, role means the degree of tension produced by moving toward a note, chord or scale other than the tonic, and how this musical tension would be eased (resolved) towards the stability of returning to the tonic chord, note, or scale (namely, function).