  An arbitrary linear relation (multivalued operator) acting from one Hilbert
space to another Hilbert space is shown to be the sum of a closable operator
and a singular relation whose closure is the Cartesian product of closed
subspaces. This decomposition can be seen as an analog of the Lebesgue
decomposition of a measure into a regular part and a singular part. The two
parts of a relation are characterized metrically and in terms of Stone's
characteristic projection onto the closure of the linear relation.
