axiom of comprehension | axiom of separation

The axiom of Zermelo-Fraenkel set theory which asserts the existence for any set a and a formula A(y) of a set x consisting of all elements of a satisfying A(y), exists x for all y(y element x congruent y element a⋀A(y)), where exists denotes exists, for all means for all, element denotes "is an element of, " congruent means equivalent, and ⋀ denotes logical AND.