ATOMIC NUMBER 18

 I. (noun) 

Sense 1

Meaning:

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

Synonyms:

Ar; argon; atomic number 18

Classified under:

Nouns denoting substances

Hypernyms ("atomic number 18" is a kind 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)

argonon; inert gas; noble gas (any of the chemically inert gaseous elements of the helium group in the periodic table)

Holonyms ("atomic number 18" is a substance of...):

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

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