1Liketherulesgoverningtheuseofshallandwillonwhichtheyarebased,thetraditionalrulesgoverningtheuseofshouldandwouldarelargelyignoredinmodernAmericanpractice.Eithershouldorwouldcannowbeusedinthefirstpersontoexpressconditionalfuturity: 　　就象作为shall和will词的基础的限用的用法规则一样,适用于should和would这个词的传统使用规则在现代美国英语中也已被忽略了.现在should或would这两个词中的任何一个都可以用于第一人称,表示条件式中的将来： 　　IfIhadknownthat,Iwould(orsomewhatmoreformally,should)haveanswereddifferently. 　　如果已经知道了这个情况的话,我就（或正规一点用should）不会那么回答了, 　　2Butinthesecondandthirdpersonsonlywouldisused: 　　但在第二人称或第三人称中只用would： 　　Ifhehadknownthat,hewould(notshould)haveanswereddifferently. 　　如果他知道那个情况的话,就（不能用should）不会那么回答了. 　　3Wouldcannotalwaysbesubstitutedforshould,however.Shouldisusedinallthreepersonsinaconditionalclause: 　　但是Would并不是总是能由should代替.Should在三种人称的条件从句中都可以用： 　　ifI(oryouorhe)shoulddecidetogo. 　　如果我（或你或他）决定要去. 　　4Shouldisalsousedinallthreepersonstoexpressdutyorobligation(theequivalentofoughtto): 　　Should用于这三种人称的表示职责和义务的句子中（相当于oughtto）： 　　I(oryouorhe)shouldgo. 　　我（或者你或者他）应该去. 　　5Ontheotherhand,wouldisusedtoexpressvolitionorpromise: 　　另一方面,would用来表达决心或保证： 　　IagreedthatIwoulddoit. 　　我一定会做的. 　　6Eitherwouldorshouldispossibleasanauxiliarywithlike,beinclined,beglad,prefer,andrelatedverbs: 　　而would或should都可以作助词和like,beinclined,beglad,prefer及其相关词语一起使用： 　　Iwould(orshould)liketocallyourattentiontoanoversight. 　　我想（或should）请你注意一下一个疏漏之处. 　　7HerewouldwasacceptableonalllevelstoalargemajorityoftheUsagePanelinanearliersurveyandismorecommoninAmericanusagethanshould.·Shouldhaveissometimesincorrectlywrittenshouldofbywriterswhohavemistakenthesourceofthespokencontractionshould've.SeeUsageNoteatif,rather,shall 　　在此处,在一次早期的调查中对大多数各阶层的使用者来说,would是可以接受的,且在美国用法中比should更为常见.有时书写者把shouldhave误拼成shouldof,因为他们把口头缩略形式should've的来源给弄错了 　　见金山词霸