Light, colorless, odorless, highly flammable gas – hydrogen combines with oxygen to form water.
Merriam-Webster Online Dictionary
hydrogen (noun)a nonmetallic element that is the simplest and lightest of the elements, is normally a colorless odorless highly flammable diatomic gas, and is used especially in synthesis - see element table compare deuterium tritium
H2, dihydrogen, molecular hydrogen, hydrogen gas, elemental hydrogen
