The Brønsted acid $\ce{BH^{+}}$ formed on protonation of a base $\ce{B}$ is called the conjugate acid of $\ce{B}$, and $\ce{B}$ is the conjugate base of $\ce{BH^{+}}$. (The conjugate acid always carries one unit of positive charge more than the base, but the absolute charges of the species are immaterial to the definition.) For example: the Brønsted acid $\ce{HCl}$ and its conjugate base $\ce{Cl^{−}}$ constitute a conjugate acid–base pair.