na-adjective, noun
monoxide
Used in chemical compound names, e.g. 一酸化炭素 (carbon monoxide).
一酸化炭素は無色無臭の気体です。
Carbon monoxide is a colorless, odorless gas.
From 一 (one) + 酸化 (oxidation), literally 'one oxidation', referring to a single oxygen atom in the compound.