define hydrogen
Full Definition of HYDROGEN. : 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 â see element table â compare deuterium, tritium.â hyÂ·drogÂ·eÂ·nous \hÄ«-Ëdrae-ËdrÃ¤-jÉ\ nÉs. adjectiveord History of HYDROGEN. When hydrogen is burned it combines with oxygen to make water. That fact accounts for the name of this gas. The word hydrogen was formed from two Greek roots. The first, hydro- , means â water, â and the second, -gen, means â giving rise to, producing.