Atomic_number_18WordNet Explorer

a colorless and odorless inert gas; one of the six inert gases; comprises approximately 1% of the earth's atmosphere

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

any of the chemically inert gaseous elements of the helium group in the periodic table

a mixture of gases (especially oxygen) required for breathing; the stuff that the wind consists of