Triads are chords made up of three notes. Triads can be major, minor, augmented, or diminished. The following examples show the structure of each of these chords:
Minor triad: minor 3rd, perfect 5th
Diminished triad: minor 3rd, diminished 5th
Augmented triad: major 3rd, augmented 5th
Major and minor triads are considered to be perfect because they always have a perfect fifth. Diminished or augmented triads are called by the name of the fifth they contain.
See C > Chord for related entries.