3  definitions  found 
 
  From  Webster's  Revised  Unabridged  Dictionary  (1913)  [web1913]: 
 
  Hydrogen  \Hy"dro*gen\,  n.  [Hydro-,  1  +  -gen:  cf  F. 
  hydrog[`e]ne.  So  called  because  water  is  generated  by  its 
  combustion.  See  {Hydra}.]  (Chem.) 
  A  gaseous  element,  colorless,  tasteless,  and  odorless,  the 
  lightest  known  substance,  being  fourteen  and  a  half  times 
  lighter  than  air  (hence  its  use  in  filling  balloons),  and 
  over  eleven  thousand  times  lighter  than  water.  It  is  very 
  abundant,  being  an  ingredient  of  water  and  of  many  other 
  substances,  especially  those  of  animal  or  vegetable  origin. 
  It  may  by  produced  in  many  ways,  but  is  chiefly  obtained  by 
  the  action  of  acids  (as  sulphuric)  on  metals,  as  zinc,  iron, 
  etc  It  is  very  inflammable,  and  is  an  ingredient  of  coal  gas 
  and  water  gas.  It  is  standard  of  chemical  equivalents  or 
  combining  weights,  and  also  of  valence,  being  the  typical 
  monad.  Symbol  H.  Atomic  weight  1. 
 
  From  WordNet  r  1.6  [wn]: 
 
  hydrogen 
  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 
  [syn:  {H},  {atomic  number  1}] 
 
  From  Elements  database  20001107  [elements]: 
 
  hydrogen 
  Symbol:  H 
  Atomic  number:  1 
  Atomic  weight:  1.0079 
  Colourless,  odourless  gaseous  chemical  element.  Lightest  and  most 
  abundant  element  in  the  universe.  Present  in  water  and  in  all  organic 
  compounds.  Chemically  reacts  with  most  elements.  Discovered  by  Henry 
  Cavendish  in  1776. 
 
 

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