except,besides,exceptfor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、everyone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"inadditionto".试比较下列例句:

　　1)HedidnothingexceptwatchTVyesterday.

　　2)Hesaidnothingexcepttosmilejustnow.

　　3)AllthestudentstookatripexceptTomyesterday.

　　4)Weneed3morepersonstofinishthejobbesides／inadditiontoustwo.

　　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)Theweatherisfinetodayexceptinthenorthwest.此句相当于:

　　Theweatherisfinetodayexceptthatitisinthenorthwest.

　　2)Hismothernevertakesanyexerciseexceptonthedancefloor.此句相当于:

　　Hismothernevertakesanyexerciseexceptthatshehasadanceonthefloor.

　　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:

　　Allthebuildingsareexcellentexceptthisone.

　　Allthebuildingsareexcellentexceptfortheirlocation或者Allthebuildingsareexcellentexceptthattheplaceonwhichthebuidingsarebuiltisnotgood.

　　2)当except用在句首时往往改用exceptfor.例如:

　　Therewasnosinglepersoninthedarkstreetthatnightexceptapolicemanonhisduty.此句相当于:

　　Exceptforapolicemanonhisduty,therewasnosinglepersoninthedarkstreetthatnight.

　　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)Tomisagoodstudentexceptthatheiscareless.此句相当于:Tomisagoodstudentexceptforhiscarelessness.

　　2)Tomseldomcomeslatetoschoolexceptwhenitrainshard.此句相当于:Tomseldomcomeslatetoschoolexceptonaheavilyrainyday.