Question

-an
I
 ( or   -ian  also   -ean)  noun suffix  
  : someone or something that belongs to
   American [=a person who lives in or is from America]
   Bostonian [=a person who lives in or is from Boston]
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II
 ( or   -ian  also   -ean)  adj suffix  
  1 : of or belonging to
   American
  2 : characteristic of : resembling
   Herculean [=resembling Hercules]
   Mozartean [=characteristic of or resembling Mozart]