Oxygen is air, the stuff we breathe, the thing that makes our lives possible. It is an element, a basic chemical found on the earth.

In fact, we don't breathe pure oxygen; our air is about 20 percent oxygen. Still, oxygen is everywhere—it’s the third most common element on earth. Usually, the word is used in scientific contexts. Still, when someone has a big personality and likes to be the center of attention, we say, they "take all the oxygen out of the room." That means they are a blowhard and attention hog. If they really took your oxygen, you’d be dead.

Definitions of oxygen
  1. noun
    a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust
    synonyms: O, atomic number 8
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    LOX, liquid oxygen
    a bluish translucent magnetic liquid obtained by compressing gaseous oxygen and then cooling it below its boiling point; used as an oxidizer in rocket propellants
    type of:
    chemical element, element
    any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter
    a fluid in the gaseous state having neither independent shape nor volume and being able to expand indefinitely
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