krypton

English Thesaurus

1. a colorless element that is one of the six inert gasses; occurs in trace amounts in air (noun.substance)

hypernym	:	chemical element, element,
definition	:	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 (noun.substance)

hypernym	:	argonon, inert gas, noble gas,
definition	:	any of the chemically inert gaseous elements of the helium group in the periodic table (noun.substance)

substance meronym	:	air,
definition	:	a mixture of gases (especially oxygen) required for breathing; the stuff that the wind consists of (noun.substance)