Ferrous (Fe²⁺), in chemistry, indicates a divalent iron compound (+2 oxidation state), as opposed to ferric, which indicates a trivalent iron compound (+3 oxidation state). This usage has mostly been deprecated, with current IUPAC nomenclature having names containing the oxidation state in bracketed Roman numerals instead, such as iron(II) oxide for ferrous oxide (FeO), and iron(III) oxide for ferric oxide (Fe₂O₃).