Define the concept of a regular expression with intersection.

Define the concept of a regular expression with intersection.

A regular expression with intersection is a type of regular expression that allows for the combination of two or more regular expressions using the intersection operator. The intersection operator, denoted by the symbol "&", is used to find the common elements or strings that are accepted by both regular expressions. In other words, it represents the set of strings that are accepted by both regular expressions simultaneously. This concept is useful in automata theory as it allows for the creation of more complex regular expressions by combining simpler regular expressions using the intersection operator.