Hi, I've got some questions about angular momentum. I hope they aren't too stupid, but I can't see the wood for the trees. Is angular momentum something that is characteristic for a particle? I know that spin is characteristic (for example, the spin of a pi- is always 0) if I'm correct, but is the spin of the combination pi+pi- always 0? And if I want to know the angular momentum of the combination of particles 123, can I group them the way I want? If I know the angular momentum of the combination 12, can I group those two particles and determine the angular momentum of (12)3? Is that the same as the angular momentum of 1(23)? Thanks!