Discrete Mathematics with Applications 4th Edition

The biconditional of p and q is "p if, and only if, q" and is denoted p $\leftrightarrow$ q. It is logically equivalent to the conjunction (p $\rightarrow$ q) $\land$ (q $\rightarrow$ p). In other words p $\leftrightarrow$ q is the same as saying both "if p, then q" and "if q, then p."