Transitive class
= Transitive class
A class $M$ is transitive when $x\in y\in M$ implies $x\in M$. Consequently, every member of a member of $M$ is available as an element of the structure $(M,\in)$.
= Transitive class
A class $M$ is transitive when $x\in y\in M$ implies $x\in M$. Consequently, every member of a member of $M$ is available as an element of the structure $(M,\in)$.