the.com/monoxide

means A compound in which one atom of oxygen is bonded to another element, most infamously carbon monoxide, the colorless, odorless gas formed by incomplete combustion.

from Built from 'mon-' (a form of the Greek 'monos', meaning 'single') plus 'oxide', itself from 'oxygen' — a word French chemists coined in the late 1700s from Greek 'oxys' ('sharp, acid') and '-gen' ('producer'), since they believed the element was essential to forming acids. 'Monoxide' simply labels the one-oxygen version of an oxide, in contrast to 'dioxide' with two — chemical bookkeeping that happens to describe one of the deadliest molecules around.