We derive an expression for a lower bound of the ground-state energy o
f N identical fermions. In principle, this relation can describe any o
rder of multiplicity of many-body forces and represents a generalizati
on of a Hall inequality. Applying the Hall lower-bound inequality to t
he Calogero and Sutherland potentials, we show the great importance of
spin states. Furthermore, using a generalized formula, we obtain a lo
wer bound for a system with three-body forces.