  We propose a new measure of relative incompatibility for a quantum system
with respect to two non-commuting observables, and call it quantumness of
relative incompatibility. In case of a classical state, order of observation is
inconsequential, hence probability distribution of outcomes of any observable
remains undisturbed. We define relative entropy of the two marginal probability
distributions as a measure of quantumness in the state, which is revealed only
in presence of two non-commuting observables. Like all other measures, we show
that the proposed measure satisfies some basic axioms. Also, we find that this
measure depicts complementarity with quantum coherence. The relation is more
vivid when we choose one of the observables in such a way that its eigen basis
matches with the basis in which the coherence is measured. Our result indicates
that the quantumness in a single system is still an interesting question to
explore and there can be an inherent feature of the state which manifests
beyond the idea of quantum coherence.
