  We have experimentally demonstrated the interferometric complementarity,
which relates the distinguishability $D$ quantifying the amount of which-way
(WW) information to the fringe visibility $V$ characterizing the wave feature
of a quantum entity, in a bulk ensemble by Nuclear Magnetic Resonance (NMR)
techniques. We primarily concern on the intermediate cases: partial fringe
visibility and incomplete WW information. We propose a quantitative measure of
$D$ by an alternative geometric strategy and investigate the relation between
$D$ and entanglement. By measuring $D$ and $V$ independently, it turns out that
the duality relation $D^{2}+V^{2}=1$ holds for pure quantum states of the
markers.
