The ‘tonic’ is the first and basic ‘tone’ of any scale.
The ‘dominant’ is the fifth degree of any scale.
The ‘mediant’ is the middle degree between the tonic and dominant
The ‘tonic’ is also the eighth degree of any scale.
The ‘sub-dominant’ is five notes below the tonic. It is also a step below the dominant.
The ‘sub-mediant’ is the middle note between the tonic (8) and the sub-dominant.
The ‘super-tonic’ is the second degree, above the tonic.
The ‘leading-tone’ is the seventh degree of any scale, and ‘leads’ to the tonic.
These functional names may be applied to any scale, major or minor. They simply indicate the position (function) of the note or chord. When describing the function (position) of notes, use Arabic numbers; 1-2-3-4, etc. When describing the function (position) of chords, use Roman numbers; I-II-II-IV, etc.
Ralph Carroll Hedges, B.Ed., B.Mus., M.M.