, in the chemical science realm, indicates a bivalent iron compound (+2 oxidation state) (as opposed to ferric
, which indicates a trivalent iron compound (+3 oxidation state)).
Outside of chemical science, 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 (which contain a few percent of carbon) and alloys of iron with other metals (such as stainless steel.)
The term non-ferrous is used to indicate metals other than iron and alloys that do not contain an appreciable amount of iron.