except,besides,except for用法的关联和区别
1.作介词用法时,这三个词都有"除…之外"的含义,但except常与do／does／did／have／has／hadnothing等词形成搭配用法,或者与全部肯定词all、everything、everyone等连用,或者与全部否定词nothing、nobody等连用,因此except加宾语作介词"除…之外"时常表示从整体中剔除一部分；而besides作"除…之外"时则表示"另外附加"的含义,相当于"in addition to".试比较下列例句:
1)He did not hing except watch TV yesterday.
2)He said nothing except to smile just now.
3)All the students took at rip except Tom yesterday.
4)We need 3 more persons to finish the job besides／inaddition to us two.
2.作介词用法时的except后可接多种情况的介词短语.在这种情况下,except后的介词是不可省去的,except加介词的实际作用就相当于连词加相关的从句.例如:
1)The weather is fine today except in the northwest.此句相当于:
The weather is fine today except that it is in the northwest.
2)His mother never takes any exercise except on the dance floor.此句相当于:
His mother never takes any exercise except that she has adance on the floor.
需要强调的是except与exceptfor的用法区别:
1)Except后排除的内容与主语往往是同一类的,而exceptfor后所排除的内容与主语往往不是同一类的.例如,试比较:
All the buildings are excellent except this one.
All the buildings are excellent except for their location或者All the buildings are excellent except that the place on which the buidings are built is notgood.
2)当except用在句首时往往改用exceptfor.例如:
There was no single person in the dark street that night except apoliceman on his duty.此句相当于:
Except for apoliceman on his duty,there was no single person in the dark street that night.
3.相当于连词用法的except与相当于连词用法的besides的区别仍然保持它们作介词用法的含义.试比较下列例句:
1)Tom is a good student except that he is careless.此句相当于:Tom is a goods tudent except for his carelessness.
2)Tom seldom comes late to school except when it rains hard.此句相当于:Tom seldom comes late to school except on a heavily rainy day.
参考资料：百度