C9 chord (also called Dominant 9th chord) for piano presented by keyboard diagrams.
Explanation: The C ninth is a five-note chord. Due to practical circumstances, however, the fifth (G) is often omitted and/or the chord is played inverted. The chord is often abbreviated as C9.
Omissions: C9(no3): C - G - Bb - D; C9(no5): C - E - Bb - D.
Theory: The C ninth chord is constructed with a root, a major third, a perfect fifth, a minor seventh and a major ninth.