Names of Degrees
Degree Name I Tonic II Supertonic III Mediant IV Subdominant V Dominant VI Submediant or
VII Leading tone
The IV degree is called subdominant because it is a fifth below the tonic while the dominant is a fifth above the tonic. The III degree is called mediant because it is midway between the tonic and the dominant. The VI degree is called submediant because it is midway between the tonic and the subdominant.