Root on A string
no fifthx-12-10-12-12-x
Am9 is the A minor 9 chord. Its notes are A, C, E, G and B. A minor seventh with a ninth. This compact grip omits the fifth.
x-12-10-12-12-x
Numbers show frets from the low E string to the high e string; x means don't play that string.
Every A, C, E, G and B on the first 12 frets. The filled dots are the root, A. Build your own shape from any nearby group.
Other A chords
Other minor 9 chords