序数词的用法总结.docx

序数词的用法总结Thesecondlessonismoredifficultthanthefirst.第2课比第1课要难。2.给东西或各种物体编号时,序号在前时用序数词,序号在后时用基数词。例如:theFifthLesson,LessonFive,No.14MiddleSchool3.序数词前面加不定冠词a/an,表示“再一”、“又一”的意思。例如:Tryitasecondtime.请再试一次。Hecastitathirdtime,anddrewinalotofstones.他又撒了第三次网,拉上来许多石头。【练一练】写出与下列基数词相应的序数词。1.one_____2.two_____3.three_____4.four_____5.five_____6.eight_____7.nine_____8.ten_____9.twelve_____10.twenty_____11.thirty-one_____12.sixty-five_____Key:1.first2.second3.third4.fourth5.fifth6.eighth7.ninth8.tenth9.twelfth10.twentieth11.thirty-first12.sixty-fifth序数词的构成方法1.一般在相应的基数词后面加词尾-th。例如:four→fourth,six→sixth,seven→seventh,ten→tenth,eleven→eleventh,thirteen→thirteenth注意下面的一些特殊变化:one→first,two→second,three→third,five→fifth,twelve→twelfth,eight→eighth,nine→ninth2.表示“几十几”或“几百零几”的基数词变为序数词时,只将个位数变为序数词,十位数或百位数不变。例如:twenty-one→twenty-first,thirty-three→thirty-third,forty-four→forty-fourth3.以-ty结尾的基数词变为序数词时,应先将y改为i,再加-eth。例如:twenty→twentieth,thirty→thirtieth,forty→fortieth,fifty→fiftieth,sixty→sixtieth,seventy→seventieth,eighty→eightieth,ninety→ninetieth4.序数词的缩略式一般由阿拉伯数字加上序数词的最后两个字母构成。例如:first→1st,second→2nd,third→3rd,fourth→4th,twelfth→12th,twenty-first→21st基数词变序数词口诀:基变序,有规律,first,second,third要牢记;其余变化有规律,基数词尾加-th;eight去t、nine去e后加-th。从twenty,thirty到ninety,需先变y为ie,再加-th;five和twelve,需将ve变f,然后再加-th。若要变成“第几十几”,只变个位就可以。--------------------------------------------------------------------------------------序数词的用法总结