Drill triad knowledge often as it lays the foundation for most popular music in which chords are employed.
Major - M3, m3
Minor - m3, M3
Augmented - M3, M3
Diminished - m3, m3
M3 = major 3rd interval (4 half steps)
m3 = minor 3rd interval (3 half steps)
Notate double sharps as a lowercase x and double flats using two lowercase b's (bb). Also, the dreaded "triple sharp", which is only found within the B# augmented chord's triad, has been notated here as #x.