  We build, using group-theoretic methods, a general framework for approaching
multi-particle entanglement. As far as entanglement is concerned, two states of
n spin-1/2 particles are equivalent if they are on the same orbit of the group
of local rotations (U(2)^n). We give a method for finding the number of
parameters needed to describe inequivalent n spin-1/2 particles states. We also
describe how entanglement of states on a given orbit may be characterized by
the stability group of the action of the group of local rotations on any point
on the orbit.
