Webster's English Dictionary

arduous

Cross references:
  1. hard                  
 
ar.du.ous \'a:rj-(*-)w*s\ aj [L arduus high, steep, difficult; akin to ON 
   o:rthigr high, steep,] Gk orthos straight 1a: hard to accomplish or achieve 
   : DIFFICULT  1b: marked by great labor or effort : STRENUOUS  2: hard to 
   climb : STEEP  - ar.du.ous.ly av

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