Naming weak conjugate bases

Oxyacids are protonated oxyanions. However, as you may know, acids dissociate into their ions in solution. Weak acids dissociate only partially to leave a hydrogenated oxyanion like HCO₃^-. The result is a weak conjugate base which we name by combining the multiplicative prefix rule from covalent compound naming with the oxyanion naming.
For example, HCO₃^- is hydrogen carbonate.

Take care; another name for hydrogen carbonate is bicarbonate. The bi- prefix is common when naming compounds with one hydrogen atom. The di- and tri- prefixes used in covalent compounds naming tend to stay unchanged.