extra in WordNet English dictionary

1. further or added
   "called for additional troops"; "need extra help"; "an extra pair of shoes"
   extra  additional 
   
2. more than is needed, desired, or required
   "trying to lose excess weight"; "found some extra change lying on the dresser"; "yet another book on heraldry might be thought redundant"; "skills made redundant by technological advance"; "sleeping in the spare room"; "supernumerary ornamentation"; "it was supererogatory of her to gloat"; "delete superfluous (or unnecessary) words"; "extra ribs as well as other supernumerary internal parts"; "surplus cheese distributed to the needy"
   excess  extra  redundant  spare  supererogatory  superfluous  supernumerary  surplus 
   
3. added to a regular schedule
   "a special holiday flight"; "put on special buses for the big game"
   extra  special 
   

1. something additional of the same kind
   "he always carried extras in case of an emergency"
   extra  duplicate 
   
2. an additional edition of a newspaper (usually to report a crisis)
   extra 
   
3. a minor actor in crowd scenes
   supernumerary  spear carrier  extra 
   

1. unusually or exceptionally
   "an extra fast car"
   extra  extra