A proper subset is denoted using the symbol and is typically used in an expression like this:

In plain language, this means that the set is a proper subset of the set . Sometimes, this is also referred to as **strict subset** notation.

A proper subset is denoted using the symbol and is typically used in an expression like this:

In plain language, this means that the set is a proper subset of the set . Sometimes, this is also referred to as **strict subset** notation.