TITLE: Confusion in symbol of subset.
QUESTION [6 upvotes]: If every element of set $A$ is an element of set $B$ then we say that $A$ is subset of $B$. $A$ is said to be proper subset if $A$ does not equal $B$.
My question is -
whether the symbol we use to show subset is  same as that for proper subset? I have seen that $A$ is subset of $A$ itself is shown by the same symbol as that for the subset while when we write improper subset, we usually write equal to sign with symbol of subset.
So, please help me to know this.

REPLY [17 votes]: As @MPW pointed out, $\subset$ is ambiguous.  My preference, therefore, is not to use this symbol at all.  I use $\subseteq$ for "subset" and $\subsetneq$ for "proper subset". So you won't encounter any ambiguities in my papers; as for other people's papers, good luck.