Half-diminished seventh chord

In music theory, the half-diminished seventh chord (also known as a half-diminished chord or a minor seventh flat five chord) is a seventh chord composed of a root note, together with a minor third, a diminished fifth, and a minor seventh (1, ♭3, ♭5, ♭7). For example, the half-diminished seventh chord built on B, commonly written as Bm7(♭5), Bø7 or Bø, has pitches B-D-F-A: It can be represented by the integer notation {0, 3, 6, 10}.

Source: Wikipedia — Half-diminished seventh chord (CC BY-SA 4.0)