If S and T are sets, the statement S=T can be expressed as...

Can someone please help me answer this question?
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If S and T are sets, the statement S=T can be experssed as:
∀x, (x∈S ⇔ x∈T)
What does S ≠ T mean? How do you go about showing that two sets are not the same?
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This is how I solved it:
∀x, (x ∉ S ⇔ x ∉ T)
But I don't think it's right.

Thank-you.

There exists an x that is an element in S and not an element in T

Or

There exists an x that is an element in T and not an element in S

Hint: To prove inequality, you don't need to say something about _all_ x. It is sufficient to say something about just one x.