Noun hydrogen has 1 sense
  1. hydrogen, H, atomic number 1 - 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
    --1 is a kind of chemical element, element; gas
    --1 is a substance of water, H2O
    --1 has particulars: tritium
    Derived form: verb hydrogenate1
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