The C half-diminished seventh chord (abbreviated "Cm7(b5) chord") is a four-note chord consisting of the notes C, E♭, G♭, and B♭. The chord is formed by lowering the fifth of a C minor seventh chord a half step.
C half-diminished seventh chord
C half-diminished chord C minor seventh flat five chord
C E♭ G♭ B♭
1 ♭3 ♭5 ♭7
Cø Cø7 Cm7b5 C–7(b5) Cmi7(b5) Cmin7(b5)
Tetrad (four-note chord)