  We test Bohr's complementary relation, which captures the most
counterintuitive difference of a classical and a quantum world, for single and
bipartite neutral kaons. They present a system that is naturally interfering,
oscillating and decaying. Moreover, kaons break the CP symmetry (C...charge
conjugation, P...parity). In detail we discuss the effect of the CP violation
on Bohr's relation, i.e. the effect on the "particle-like" information and the
"wave-like" information. Further we show that the quantity that complements the
single partite information for bipartite kaons is indeed concurrence, a measure
of entanglement, strengthening our concept of entanglement. We find that the
defined entanglement measure is independent of CP violation while it has been
shown that nonlocality is sensitive to CP violation.
