(inorganic chemistry) A non-flammable gas (N₂O) commonly used in surgery and dentistry for its anaesthetic and analgesic effects.

(organic chemistry) The simplest epoxide; used as a sterilizing agent and in the production of ethylene glycol.

(chemistry) Any substance that oxidizes, or receives electrons from, another; in so doing, it becomes reduced.

(chemistry) the state of an atom having a particular oxidation number

(chemistry) The compound obtained by the reaction of oxygen on iron. Either iron(II) oxide (old term ferrous oxide, chemical formula FeO) or iron(III) oxide (old term ferric oxide, chemical formula Fe₂O₃). Generally known as rust when hydrated.

(chemistry) any compound having the general formula R₃P=O <=> R₃P⁺O⁻

(chemistry) a white, powdered alkali, Li₂O, used in the manufacture of glass and ceramics

(inorganic chemistry) A white, crystalline compound, BeO, used in semiconductors and in specialist ceramic applications.

(chemistry) An aminoxyl radical.

(organic chemistry) An arene epoxide.