A 11th chord
A11 chord for piano presented by keyboard diagrams.
Explanation: The A eleventh is a six-note chord. To avoid dissonance the third (C#) is normally omitted. The chord is also often played inverted. The chord is abbreviated as A11.
Theory: The A eleventh chord is constructed by adding a third to a ninth chord.
Notes: A - C# - E - G - B - D