Ferrous in chemistry indicates a divalent iron compound as opposed to ferric, which indicates a trivalent iron compound .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).
Outside chemistry, ferrous is an adjective used to indicate the presence of iron. The word is derived from the Latin word ferrum ("iron").Ferrous metals include steel and pig iron (with a carbon content of a few percent) and alloys of iron with other metals (such as stainless steel). Manipulation of atom-to-atom relationships between iron, carbon, and various alloying elements establishes the specific properties of ferrous metals.
The term non-ferrous is used to indicate metals other than iron and alloys that do not contain an appreciable amount of iron.