The D dominant ninth chord is a 5-note chord consisting of the notes D, F#, A, C and E.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as D9.
Chords that are a superset of D9. The chords include more notes but always D, F#, A, C and E.
Chords that are a subset of D9. These contain less notes but all of them are included in D9.
In case you prefer a non-interactive variant of the chord chart, we've embedded a PNG image below that shows the notes for the the D9 chord. Feel free to save or share the image as needed.