函 
函 ³hán {E} n. 〈wr.〉 ①case; big envelope; casket ②letter
函 函 [hán] envelope; case; letter 信函 信函 ④ [xìnhán] letter; mailbox 致函 致函 [zhìhán] send a letter 函授 函授 ⑤ [hánshòu] to teach by correspondence 来函 来函 [láihán] incoming letter; letter from afar; same as 来信 函件 函件 [hánjiàn] letters; correspondence 公函 公函 [gōnghán] official letter 
公 公 public / - / enter elbow public 函 函 bin / - / snare sparkler shovel bin 函授