Merriam-Webster Collegiate Dictionary - oxygen

 noun  Usage: often attributive  Etymology: French oxygene, from Greek oxys, adjective, acidic, literally, sharp + French -gene -gen; akin to Latin acer sharp — more at edge  Date: 1788  1. a reactive element that is found in water, in most rocks and minerals, in numerous organic compounds, and as a colorless tasteless odorless diatomic gas constituting 21 percent of the atmosphere, that is capable of combining with all elements except the inert gases, that is active in physiological processes, and that is involved especially in combustion — see element table  2. something that sustains or fuels disagreement is the true ~ of these magazines — Joseph Epstein  • ~less adjective