twelve的序数词。大家好，我是张老师，今天为大家总结小学英语中基数词和序数词的的含义与用法，如果对你有帮助请关注收藏，谢谢大家！
1.基数词
(1) 基数词在句中主要用作主语、宾语、定语、表语。
eg. Thirty of them are Party members.(主语)
—How many would you like?
—Three, please.(作宾语)
The nine boys are from Tianjing.(定语)
Six plus four is ten.(表语)
(2) 表示一个具体数字时，hundred, thousand, million一律不用复数，在表示一个不确定数字时则用复数。
eg. Our country has a population of 1,300 million people.
There are three thousand students in our school.
After the war, thousands of people became homeless.
Maize is the most important food crop for millions of people in the world.
They arrived in twos and threes.
2.序数词
（1）序数词主要用作定语，前面要加定冠词。
eg. The first truck is carrying a foot baskets. John lives on the fifteenth floor.
（2）由几个序数词和基数词在拼写时不对应，很容易写错，应特别注意，它们是one- first, two- second, three- third, five- fifth, eight- eighth, nine- ninth, twelve-twelfth
（3）表示年月日时，年用基数词表示，日用序数词表示。
eg. 1949年十月一日，读作: October (the) first, nineteen sixty.
2004年九月十日，读作: September(the) tenth, two thousand and four.
（4）表示分数时，分子用基数词，分母用序数词表示。分子大于1时，分母加s.
eg. three fourths. one second, two fifths
（5）序数词有时用缩写形式
first—1st, second-2nd, third-3rd. fourth-4th, twenty-second—22nd
【难点】
（1） 表示”……+”的数词的复数形式可用来表示人的岁数或年代。
eg. He is in his early thirties. He died still in his forties. This took place in 1930s.
（2）表示时刻用基数词.
We get up at six. The workers begin to work at eight.
表示“几点过几分”用介词past, 但须在半小时以内。
eg. ten past ten. a quarter past nine. half past twelve.
表示“几点差几分”用介词to, 但分数必须在半小时以上。
eg. twenty to nine. five to eight. a quarter to ten
表示“几点几分”还可直接用基数词。
eg. seven fifteen. eleven thirty nine twenty
（3）序数词有时前面可加不定冠词来表示“再一”，“又一”这样的意思。
eg. We will have to do it a second time. Shall I ask him a third time?
When I sat down, a fourth man rose to speak.
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