A seventh chord is formed by adding an interval of a seventh to the root note of a triad:

Dominant seventh chord

The most common type of seventh chord is the dominant seventh chord. It is found in the V degree of major scales. It consists of a major triad and a minor seventh:

Major seventh chord

A major seventh chord (a major triad and a major seventh) is found in the I and IV degrees of major scales:

Minor seventh chord

The minor seventh chord (a minor triad and a minor seventh) is found in the II, III, and VI degrees of major scales:

Half-diminished seventh chord

The half-diminished seventh chord (a diminished triad and a minor seventh) is found in the VII degree of major scales.:

Diminished seventh chord

The diminished seventh chord (a diminished triad and a diminished seventh) is found in the VII degree of harmonic minor scales:

Inversions

Since seventh chords have four notes, they can have up to three inversions:

This table summarises these five types of seventh chord:

Chord	Triad type	Seventh interval	Chord symbol
Dominant seventh	Major	Minor seventh	C7
Major seventh	Major	Major seventh	CMaj7	CMa7	C▵
Minor seventh	Minor	Minor seventh	Cm7	C-7	Cmin7
Half-diminished seventh	Diminished	Minor seventh	Cm7(b5)	Cø
Diminished seventh	Diminished	Diminished seventh	Cdim7	Co7