  Leibniz algebras are certain generalizations of Lie algebras. Motivated by
the concept of subinvariance in group theory, Schenkman studied properties of
subinvariant subalgebras of a Lie algebra. In this paper we define subinvariant
subalgebras of Leibniz algebras and study their properties. It is shown that
the signature results on subinvariance in Lie algebras have analogs for Leibniz
algebras.
