  We introduce a complete set of complementary quantities in bipartite,
two-dimensional systems. Complementarity then relates the quantitative
entanglement measure concurrence which is a bipartite property to the
single-particle quantum properties predictability and visibility, for the most
general quantum state of two qubits. Consequently, from an interferometric
point of view, the usual wave-particle duality relation must be extended to a
``triality'' relation containing, in addition, the quantitative entanglement
measure concurrence, which has no classical counterpart and manifests a genuine
quantum aspect of bipartite systems. A generalized duality relation, that also
governs possible violations of the Bell's inequality, arises between single-
and bipartite properties.
