  We present a general description of separable states in Quantum Mechanics. In
particular, our result gives an easy proof that inseparabitity (or
entanglement) is a pure quantum (noncommutative) notion. This implies that
distinction between separability and inseparabitity has sense only for
composite systems consisting of pure quantum subsystems. Moreover, we provide
the unified characterization of pure-state entanglement and mixed-state
entanglement.
