ETYM Latin medians, p. p. of mediare to halve: cf. Italian mediante, French médiante.
(Music) The third note of a diatonic scale; midway between the tonic and the dominant.
In music, the third note (or degree) of the diatonic scale, for example E in the C major scale. A chord of the mediant is a triad (chord of three notes) built upon the mediant note.