We study the connection
between two combinatorial notions associated to a quiver: the quiver algebra and the
path coalgebra. We show that the quiver coalgebra can be recovered from the quiver
algebra as a certain type of finite dual, and we show precisely when the
path coalgebra is the classical finite dual of the quiver algebra, and when all
finite-dimensional quiver representations arise as comodules over the path coalgebra.
We discuss when the quiver algebra can be recovered as the rational part of the dual
of the path coalgebra. Similar results are obtained for incidence (co)algebras. We
also study connections to the notion of coreflexive (co)algebras, and give a
partial answer to an open problem concerning tensor products of coreflexive
coalgebras.