The property of a propositional logic with a conditional connective $\to$ such that $\phi \to \psi$ is a theorem of the logic only if the formulae $\phi$ and $\psi$ have a propositional parameter in common. The common parameter appearing in $\phi$ and $\psi$ can be regarded as entailing that the meanings of $\phi$ and $\psi$ will overlap and guarantee relevance of one to the other. Satisfaction of the variable sharing property is frequently considered to be the defining feature for a deductive systems to be considered a relevant logic. Nevertheless, as stronger criteria exist—such as depth relevance—systems enjoying the property are sometimes known as weakly relevant.