1.besides 和 in addition to 同义,表示“除……之外(还)……”.
如：She knows Japanese besides English.
= In addition to English,she knows Japanese.
2.但是当与nothing,nobody或no one等否定意义的不定代词连用时,besides与except同义,表示“除…之外(其余都不)”,此时一般不用in additon to.
如：All of them went to climb the mountain except/besides me.