An eleventh chord is created by adding an 11th degree to any dominant 9th chord. For example, a C11 chord contains the notes C, E, G, Bb, D and F (1, 3, 5, b7, 9 and 11). The 3rd degree is usually omitted because of its clash with the 11th degree. Here are some common open 11th chord shapes.
C11

Db11

D11

Eb11

E11

F11

F#11

G11

Ab11

A11

Bb11

B11
