 This approach (called "semicomplementation") is well-defined even for a (meet) semilattice; if the set of semicomplements has a greatest element it is usually called pseudocomplement.If the pseudocomplement satisfies the law of the excluded middle, the resulting algebra is also Boolean.However, if only the weaker law ¬"x" ∨ ¬¬"x" = 1 is required, this results in Stone algebras.