In the reaction $\mathrm{HCl}+{\mathrm{H}}_2\mathrm{O}\rightleftharpoons {\mathrm{H}}_3{\mathrm{O}}^{+}+{\mathrm{Cl}}^{-}$

${\mathrm{H}}_3{\mathrm{O}}^{+}$ is the conjugate base of $\mathrm{HCI}$

${\mathrm{H}}_2\mathrm{o}$ is the conjugate base of $\mathrm{HCI}$ acid 

${\mathrm{Cl}}^{-}$ is the conjugate acid of ${\mathrm{H}}_2\mathrm{O}$ base

${\mathrm{Cl}}^{-}$ Is the conjugate base of $\mathrm{HCl}$ acid