c++ - 'SystimaDieythynsis' & 'Mihani' does not name a type -

the title explains question, why won't compile?

class vehicle {   private:      char* idioktitis,arkykloforias;     int etoskat;     systimadieythynsis sysdief;     mihani eng;  };  class mihani {  private:      int kyvismos,ippodynami; public:      void leitourgia();     void kinisi();     void svysimo(); };  void systimadieythynsis::vazeiempros(){      cout << "bazei empros"; }  void systimadieythynsis::svynei(){      cout << "svynei"; }  void systimadieythynsis::striveiaristera(){      cout << "strivei aristera"; }  void systimadieythynsis::striveidexia(){      cout << "strivei dexia"; }  void mihani::leitourgia(){      cout << "leitourgia mhxanhs";  }  void mihani::kinisi(){      cout << "kinhsh mhxanhs";  }  void mihani::svysimo(){      cout << "svhsimo mhxanhs";  }  int main(int argc, char *argv[])  {     system("pause");     return exit_success;  } 

you need add class definition systimadieythynsis , place , class definition mihani before class definition vehicle. so:

class mihani {      // ... };  class systimadieythynsis {     // ... };  class vehicle {     // ... };  // insert function definitions here