duplicate in WordNet English dictionary

1. increase twofold
   "The population doubled within 50 years"
   double  duplicate 
   
2. make or do or perform again
   "He could never replicate his brilliant performance of the magic trick"
   duplicate  reduplicate  double  repeat  replicate 
   
3. make a duplicate or duplicates of
   "Could you please duplicate this letter for me?"
   duplicate 
   
4. duplicate or match
   "The polished surface twinned his face and chest in reverse"
   twin  duplicate  parallel 
   

1. a copy that corresponds to an original exactly
   "he made a duplicate for the files"
   duplicate  duplication 
   
2. something additional of the same kind
   "he always carried extras in case of an emergency"
   extra  duplicate 
   

1. being two identical
   duplicate  matching  twin  twinned 
   
2. identically copied from an original
   "a duplicate key"
   duplicate