序数词前冠词的用法规律
规律1、序数词前用定冠词
在一般情况下，序数词前要用定冠词。如：
Read your book, starting at the second paragraph.朗念书本，从第2段读起。
We especially enjoyed the third act of the play. 大家特别喜欢戏的第3幕。
The boxer gave in at the fifteenth round. 这个拳击师在第15个回合中认输了。
I can find seven, but where is the eighth plate? 我能找到7个盘子，第8个在什么地方呢？
Skip the first chapter and start on page 25. 跳过第1章，从第25页开始看。
He’s going to compete with his old rival in the second round.第2回合时他将与老对手角逐。
规律2、序数词前用不定冠词
在序数词之前有时用不定冠词a ，用以表示数目或序数的增加。如：
Do you want to read it a third time? 你还想看第3次吗？
I’d like a second helping, I’m still hungry! 我想再来一份，我还饿着呢！
Several candidates were called for a second interview. 有几个候选人被叫来作第二次面试。
He gave her another sedative. Then a third. 他给了她另一片镇静剂，接着又给了一片。
They proposed a third formula for the new swimming pool. 他们为新游泳池提出了第3种策略。
规律3、序数词前用物主代词
当序数词前有物主代词修饰时，其前不可以再用冠词。如：
She’s his second wife. 她是他的第二个老婆。
This makes our third party this month. 这算大家这个月第3次聚会了。
This was her third conviction for cheating. 这是她第3次被判犯有欺诈罪。
I can dimly remember my fourth birthday. 我隐约记得自己过4岁过生日时的情景。
To be honest, my second pregnancy was an accident. 说实话，我的第二次怀孕是个意料之外。
规律4、不需要序数词来表示序数
有的汉语中的序数在英语中并未必要用序数词来表示。如：
I read Chapter 11. 我读了第11章。
All candidates must attempt Questions 1-5. 所有考生均须回答第1-5题。
Everybody, we begin at page 50 today.各位，大家今天从第50页开始。
Act Two begins with a short dialogue between father and son. 第2幕以父子间的一段小对话开始。
I live in the last house but two in this street. 我住在这条街上倒数第3座房屋里。
The newspaper ran the review on page four. 报纸把这则评论刊登在第4版上。
