Why does an anion ending in -ite produce an acid name ending in -ous?

In the nomenclature of oxyacids, the naming convention is based on the name of the polyatomic anion it contains. When an anion ends in -ite, the corresponding acid is named by replacing the -ite suffix with -ous.1

This system is designed to reflect the relationship between the number of oxygen atoms in the anion and the resulting acid. Oxy anions that contain fewer oxygen atoms are assigned the -ite suffix, while those with more oxygen atoms end in -ate. Consequently, when these anions form acids by bonding with hydrogen cations, the suffix is modified to distinguish the acid's composition:23

• -ite anions (fewer oxygen atoms) become -ous acids (e.g., sulfite becomes sulfurous acid).1
• -ate anions (more oxygen atoms) become -ic acids (e.g., sulfate becomes sulfuric acid).1

This standardized naming helps chemists identify the oxidation state and oxygen content of the acid based on its name.41