in addition 另外,相当于一个副词,后面一般连接句子,
eg.In addition,they lack courage.此外,他们还缺乏勇气.
in addition to 除...之外,相当于一个介词,后接名词或动词ing形式,eg.In addition to all of the above,she win a Pulitzer prize in 1980.
除上述外,她还在一九八○年获得普立兹奖.
besides 和 in addition to 同义,表示“除……之外(还)……”.