Chord of 3 notes, basically a ‘root’ and the notes a third and a fifth above it, forming two superimposed thirds, e.g. C–E–G (‘common chord’ of C major). If lower third is major and the upper minor, the triad is major. If lower third is minor and the upper major, the triad is minor. If both are major the triad is augmented. If both are minor, the triad is diminished.