664. What character can be added to both of these characters to give other characters? 折_ -> _鳥

Answer:

折  SETSU, o(ru), o(reru), ori - break, fold, yield, bend, occasion

鳥  CHOU, tori - bird 

Add 口:折+口 口+鳥 

口  KOU, kuchi - mouth

哲  TETSU - wisdom

鳴  MEI, na(ku), na(ru)(rasu) - cry, sing, howl, ring