# What is this symbol used for?

I have seen the symbol $\subsetneqq$ in a Probability exercise. What is it used for? In the exercise it seemed to mean "proper subset of", but then in what is it different from $\subsetneq$?

• It's equivalent, just another choice of notation. – aes Nov 22 '14 at 20:22
• It has the same meaning as $\subsetneq$, but the strike-through in $\subsetneqq$ is more difficult to overlook. – Daniel Fischer Nov 22 '14 at 20:22