Mediant

Mediant 

in music, the designation for chords that are a third above or below the tonic, that is, at the third (III) and sixth (VI) degrees of the major or minor scale.

In its more restricted meaning, the mediant (or upper mediant) denotes the chord of the III degree (the chord of the VI degree in this case is called the submediant, that is, the lower mediant). The same terms are used to designate the corresponding tones, that is, III and VI degrees of the scale. The mediant chords occupy an intermediary position between the basic ones: III between I and V; VI between I and IV. From this is derived the dual function of the mediant chords: III is a weakly expressed dominant, VI a weakly expressed subdominant. At the same time, III and VI can fulfill some functions of the tonic. This also determines the expressive significance of the mediant chords, their softened and veiled contrast with the tonic, and the softness of the changes in the third when a joining with the tonic, subdominant, and dominant occurs.

IU. N. KHOLOPOV