数 词,数词的定义 数词是表示数目多少或先后顺序的词,有基数词和序数词两种。表数量的数词叫基数词，如one, two, three,表顺序的数词叫序数词，如first, second, third, fourth, fifth,.,基数词 构成 1）112单独记one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve 2)1319词尾为-teen：thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen 3)2090逢整十词尾为-ty：twenty, thirty, forty, fifty,. 4)21 99在十位数和个位数之间加连字符构成，如：73 seventy-three, 88 eighty-eight,5)101 999先说几百，再加and,再加末尾两位数，如：178 one hundred and seventy-eight 6)1000以上的数词，先从后向前数，每三位用一个数逗点“，”隔开。第一个“，”是thousand千，第二个“，”是million百万，第三个“，”是billion美语中的十亿（英国用thousand million），然后一节一节地用几百几十几的方法来数。,基数词的使用 基数词可在句中作主语、表语、定语、状语、介宾、同位语。 Two of them are students.主语 Two and two are four. 表语 We two joined the army.同位语 Two thousand people were present at the meeting.定语,基数词使用的注意事项 1）hundred, thousand, million, billion, score(20),dozen(12)前有数词表示具体数目时，这些词不加“s”。当其前无具体数词时，这些数词要加“s”后再加of 连接名词，来表示不具体的量。 如：five hundred people, two score apples, hundreds of people, scores of pears, thousands of, thousands and thousands of, tens of thousands of, millions of, a few hundred men, many thousands of men, some/several million(s of) men,2)表示“几十”的数词的复数形式前用形容词性物主代词修饰可用来表示“在某人十几岁时”；用定冠词修饰表示“年代”。 in ones early twenties (thirties) 在某人二十（三十）几岁时 the 1840s/the 1840s 19世纪40年代 the 1980s/the 1980s 20世纪80年代,十亿以上的大数，英美有不同的表示：英国英语 美国英语 十亿thousand million one billion 百亿ten thousand million ten billion 千亿hundred thousand million one hundred billion 万亿one thousand billion one trillion,年代的读法:297读作two ninety-seven或two hundred and ninety-seven1908读作nineteen and eight或nineteen o eight或nineteen hundred and eight1949读作nineteen forty-nine或nineteen hundred and forty-nine2000读作two thousand,3)a.在美国英语中，表示几点过几分可用after,表示几点差几分可用before。如12点10分：ten after twelve。11点50分：ten before twelve。 b.若想表明是上午，可在时间后加上am或a.m. (a.m.是拉丁语ante meridiem的缩写，意为“上午”)，若想表明是下午，可在时间后加上pm或p.m. (p.m.是拉丁语post meridiem的缩写意为“下午”)。a.m.或p.m.前若是整点，用了a.m.或p.m后，不再用oclock，也不可加 “：00 ”。如：at 8 a. m.（上午8点），at 5 p. m.（下午5点）。,c.表示“点整”时，用sharp。如: at nine oclock sharp（九点整），at 23:00 sharp（二十三点整）。,4)年龄表达表示“岁” He is eighteen (years old). He is aged eighteen. He is at the age of eighteen. His age is eighteen.表示“快满岁”He will be eighteen years old. He is going on eighteen years old. He is getting on for eighteen.It will be his eighteenth birthday.,表示“不满岁” He is barely/nearly/almost eighteen. He is not quite/yet eighteen. He is under/below eighteen. 表示“已经岁”可用以下方法表示： He is past/over/above eighteen. He is more than eighteen. He has turned eighteen.,表示大概年龄时用“in ones +基数词复数形式”结构。 a.从十三岁到十九岁，用in ones teens . b.二十岁以上就用in ones twenties/thirties/forties/ fifties / nineties，还可以借助early，middle，late来表达得更明确一些。,序数词 基数词变为序数词,记忆口诀 一二三要单独记：onefirst, two second, three third th要从四加起：four fourth, five fifth,. eight少个t：eight eighth nine去掉e：nine ninth ve用f来代替：five fifth, twelve twelfth ty变成tie：twenty twentieth 表第“几十几”，基数加序数记心里： twenty-onetwenty-first,序数词的使用 1. 序数词在句中主要作定语，一般情况下序数词前要加定冠词。 Monday is the second day of a week. 星期一是一周的第二天。 2. 序数词前有时加不定冠词，表示“又一、再一”，相当于another。 Would you like a second cup of tea? 你还想再来一杯茶吗？ I had a fourth apple.我(吃了三个苹果后)又吃了一个苹果。,3. first, second等有时可表示一批人或物。The first milu deer came from China in the 1860s.最早的麋鹿是在十九世纪六十年代来自中国的。 4. 有时序数词作状语，不加冠词。He came out first in the contest. 他在比赛中获得第一名。 5. first, second等在用来指“冠军、亚军”等获胜名次时也常不加冠词。 He is first.他是冠军。,数词的使用 一、 百分数、分数、小数的构成及用法 1)百分数：基数词加百分号（percent）: 89%eighty-nine percent 2)分数：分子基数词，分母序数词。分子大于1，分母用复数。1/3: one third, 2/5: two fifths,3)带分数：基数词 + and +分数表达： : five and six-sevenths 注意 1/2: a half, one half 1/4: one-fourth, one /a quarter3/4: three quarters1/3: a third(33.33r %读作 thirty-three point three three recurring percent) 4）小数：小数点读作“point”，数字一律用基数词1.45: one point four five,5)通常分数、百分数、小数作定语。“分数（百分数）（of） +名词”作主语时谓语动词是根据名词确定的，名词为单数动词即用单数，名词为复数动词即用复数动词。50% apples are here.One third apple is eaten. one and a half后的名词用复数，谓语动词一般用单数，不过事实上也可用复数。,倍数表达表示倍数时，一倍用once，两倍用twice，三倍以上用“基数词+times”。1.常用句式： .times+ 形容词/副词的比较级than. .times as+形容词/副词原级+as+.,times the size/length/height/width/.of+ n.表示 Li Ming runs twice faster than Lily.The river is three times longer than that one.= The river is four times as long as that one.Our classroom is four times as big as yours.= Our classroom is three times bigger than yours.The new building is four times the size of the old one,2.有时我们用这三个句型的变体 1)“.times as many/much + n. + as + n.”或 “.times as much/many as + n.” We have produced twice as many cars this year as we expected. 我们今年生产的汽车是预期的两倍。 There are four times as many books in our library as in theirs.我们图书馆的书是他们图书馆的四倍。 The price of this product is twice as much as that of the previous one. 该产品的价格是前一种的两倍。,2) .times +more+名词+than+被比较对象He earns five times more money than he did ten years ago.他现在挣的钱是十年前挣的五倍。 3) .times +that of +被比较对象The size of the newly broadened square is four times that of the previous one. 新扩建的广场是以前的四倍大。 The hospital charges three to five times that of ordinary ones 这家医院的收费是一般医院的三至五倍。,