hydrogen

Definitions of hydrogen
1

n a nonmetallic univalent element that is normally a colorless and odorless highly flammable diatomic gas; the simplest and lightest and most abundant element in the universe

Synonyms:
H, atomic number 1
Types:
tritium
a radioactive isotope of hydrogen; atoms of tritium have three times the mass of ordinary hydrogen atoms
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
gas
a fluid in the gaseous state having neither independent shape nor volume and being able to expand indefinitely

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