小学英语知识点——数词
数词表示数量或顺序的词叫做数词。英语的数词可以作句子的主语、宾语、表语和定语。
朗诵三字经1、数词：
(1)基数(Cardinal numerals)：one，two，
(A)除one接单数名词外，其余均接复数名词。
He has one sister and three brothers.
(B)hundred的后面须加and（但可以省略）。
12，345=twelve thousand three hundred(and)forty five；
(2)序数(Ordinal mumerals)：first，cond，
听英语翻译 (A)序数前面必须附以定冠词。而a cond，a third等，则是another的意思。
(B)日期多用序数。
It’s on Friday，the fifth of October(=October the fifth=October 15th).
(C)序数的简体。
9th=the ninth；12th=the twelfth；16th=the sixteenth；
(3)分数：
(A)分数的表示法：第一，分子用基数，分母用序数。第二，分子大于2时，分母须加“s”以形成复数。
1/2=a(one)half；1/3=a(one)third；2/3=two-thirds；1/4=a(one)quarter；
(B)分数可接与不可数名词；所接的名词是单数，则与单数动词连用，是复数则与复数动词连用。
A third of the peach was bad.我爱的人他不爱我
A third of the bananas were bad.
(4)倍数词：常用的有half，double，treble（三倍）等。
(A)half a，a half，half the＋名词，表（一半的）。
适合客厅的挂画 He ran a half mile in half an hour.
He ran half a mile in half an hour.
I have read half the book.
(B)half还可作名词，代名词及副词。
电影2012
Two halves make a whole.（名词）
This is half as much again as that.（副词）
(C)倍数常用的表达法：
(half；double；treble；twice；two times；three times；)＋定冠词或所有形容词＋名词或所有代名词
I had to pay double(=twice)the usual fare.
That window is three times the size of this.
2、“数词＋名词”结合而成的形容词：
(1)数词＋名词＝形容词
a five-dollar bill；
two three-hour periods；美丽如斯
价格承诺 the Three-power Conference(三强会议)；
(2)数词＋名词＋形容词＝形容词
a six-year-old boy；西红柿土豆
a three-hundred-year-old tree；
注：上述的复合字是以hyphen(-)连结，而且其中的名词要用单数形式。
(3)名词（无冠词）＋基数＝the＋序数＋名词
World WarⅡ=World War Two or the Second World War；
Vol.Ⅰ=Volume One or the First Volume；
Page 4=page four or the fourth page；
Lesson 6=lesson Six or the Sixth Lesson；
Chap.Ⅲ=Chapter Three or the Third Chapter；
