  Vectorial forms of structured light that are non-separable in their spatial
and polarisation degrees of freedom have become topical of late, with an
extensive toolkit for their creation and control. In contrast, the toolkit for
quantifying their non-separability, the inhomogeneity of the polarisation
structure, is far less developed, and in some cases fails altogether. To
overcome this, here we introduce a new measure for vectorial light, which we
demonstrate both theoretically and experimentally. We consider the general case
where the local polarisation homogeneity can vary spatially across the field,
from scalar to vector, a condition that can arise naturally if the composite
scalar fields are path separable during propagation, leading to spatially
disjoint vectorial light. We show how the new measure correctly accounts for
the local path-like separability of the individual scalar beams, which can have
varying degrees of disjointness, even though the global vectorial field remains
intact. Our work attempts to address a pressing issue in the analysis of such
complex light fields, and raises important questions on spatial coherence in
the context of vectorially polarised light.
