  A subalgebra B of a Lie algebra L is called a weak c-ideal of L if there is a
subideal C of L such that L = B+C and B\cap C \subseteq B_L where B_L is the
largest ideal of L contained in B. This is analogous to the concept of weakly
c- normal subgroups, which has been studied by a number of authors. We obtain
some properties of weak c-ideals and use them to give some characterisations of
solvable and supersolvable Lie algebras. We also note that one-dimensional weak
c-ideals are c-ideals.
