- a colorless, slightly water-soluble gas, NO, formed by the action of dilute nitric acid on copper, and by the direct combination of atmospheric oxygen and nitrogen at the high temperatures of an electric arc: an intermediate in the manufacture of nitric acid.
- a colourless slightly soluble gas forming red fumes of nitrogen dioxide in air. Formula: NOSystematic name: nitrogen monoxide
- A colorless, poisonous gas produced as an intermediate compound during the manufacture of nitric acid from ammonia or from atmospheric nitrogen. It is also produced through cellular metabolism. In the body, nitric oxide is involved in oxygen transport to the tissues, the transmission of nerve impulses, and other physiological activities. Chemical formula: NO.