In English, this says: Given any set x, there is a set y such that, given any set z, this set z is a member of y if and only if every element of z is also an element of x.
In English, this says: Giv.en any set x, there is a set y such that, given any !set z, this set z is a member of y if and only if every elem?en!t of z is also an elem?ent of x.