Chord Structures

The most common chords beyond triads are ones that employ a 7th. Yes, that would be a triad with a 7th scale degree. These are called 7th chords. These are the 4 most popular:

Dominant 7th: M3 with a m3, and a m3 on top.
Ex: G7

Major 7th: M3 with a m3, and a M3 on top.
Ex: FΔ7

Minor 7th: m3 with a M3, and a m3 on top.
Ex: Am7

Half-Diminished 7th: m3 with a m3, and a M3 on top.
Ex: Bø7

Fully-Diminished 7th: m3 with a m3, and a m3 on top.
Ex: Bo7