Let's take a look at some common 9 and altered (sharp or flat) 9 chord shapes. Each of the examples below will have the same root note of D for comparison purposes.
9 chords are constructed with the 1st, 3rd, 5th, b7th, and 9th notes of the major scale. D9 contains D, F#, A, C, and E.
The shape above omits the 5th (A), which is common in jazz chord shapes.