推荐回答（1个）
英语中，使用序数词时前面要加定冠词 the，但在下面的情况下则不加 the:
1.当序数词前有形容词性物主代词或名词所有格修饰时，序数词前不用 the。
Mother was my first teacher in my life.妈妈是我生命中的第一个老师。
2.当表达分数时，序数词前不用 the。
One fifth of the students here are from the country. 这儿1/5的学生来自农村。
3.当表达"又一，再一"时，序数词前不用 the，但可加不定冠词。
Please give me a second chance. 请再给我一次机会。
4.当表达"年月日"时，尤其在朗读时，序数词前要加 the。但当书写时,序数词前不用the。
He was born on June 6th, 1974. 他出生在1974年6月6日。
5.当序数词在句中作状语时，序数词前不用 the。
Who got there second? 谁第二个到那儿的?
6. 当表达考试(赛跑等)中获得的名次时，序数词前不用 the。
She stands first in her class. 她在班上成绩排名第一。
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