Now, we've defined the equivalence point to be the point at which all the acid has been neutralized. So every single molecule of acid in our buffer system has been neutralized. Now, we can also define something called the half equivalence point. And the half equivalence point is the point at which exactly half of the acid in our buffer system has been neutralized. Now, suppose we choose our buffer system to consist of acetic acid. Now, acetic acid associates it to acetate ion and an H plus ion.