What is a Half-Diminished?

A half-diminished chord is a four-note chord that consists of a root, minor third, diminished fifth, and minor seventh. It is often written as m7♭5 or with the symbol ø. This chord has a darker and more unstable sound than a minor chord but is less tense than a fully diminished seventh chord.

For example, a B half-diminished chord (Bø or Bm7♭5) contains the notes B, D, F, and A. The interval between the root and the fifth is diminished (B to F), and the seventh is a minor seventh above the root. These intervals give the chord its characteristic slightly tense and unresolved quality.

Half-diminished chords commonly appear in jazz, classical harmony, and minor key progressions. In classical music, they often function as the viiø7 chord in minor keys, leading toward the dominant or tonic. In jazz, they are frequently used in ii–V–I progressions in minor keys, where they help create smooth harmonic movement.