The symbolism A = {x: p(x)} is read, “A is (or equals) the set of all x such that p(x) is true,” and it can be asserted that: if p(x) is true then x ∈ A, else x ∉ A, or, if y is any other thing different from x, then it can also be asserted that: if p(y) is true then y ∈ A, else y ∉ A.
