介词是通常位于名词或代词之前的词。(关于介词的其他位置，参见第87节。)介词之后也可以接动词(但除了在but和except之后)，该动词必须用动名词形式：
He is talking of emigrating.
他正在谈论移居国外的事。
They succeeded in escaping.
他们得以逃脱。
学生在介词方面有两个主要问题。他必须弄清楚：
(a)在某一个结构中是否需要介词;
(b)如需要介词，要用哪一个。
第一个问题对于欧洲学生来说特别棘手。他可能发现母语中某一结构需要介词而英语中的一个类似结构却不需要，反之亦然，如在欧洲的大多数语言中目的由一个介词+不定式来表示，而在英语中只由不定式表示：
I came here to study.
我到这里来学习。
学生还应该注意，许多主要用做介词的词也可以用做连词及/或副词。这种情况将在以下各节一一指出。
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2015秋鲁教版英语八上Unit 1《Could you please clean your room》（SectionB 1a-2e）word教案
2015秋鲁教版英语八上Unit 5《What’s the highest mountain in the world》（SectionB 1a-1d）word学案
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2015秋鲁教版英语八上Unit 1《Could you please clean your room》（SectionB 2a-3b）word学案
2015秋鲁教版英语八上Unit 2《Why don’t you talk to your parents》（SectionA 3a-3c）word教案
2015秋鲁教版英语八上Unit 4《An old man tried to move the mountains.》（SectionA Grammar-4a）word教案
2015秋鲁教版英语八上Unit 3《What were you doing when the rainstrom came》（SectionA 1a-2d）word教案
2015秋鲁教版英语八上Unit 3《What were you doing when the rainstrom came》（self check）word学案
2015秋鲁教版英语八上Unit 4《An old man tried to move the mountains.》（SectionA 1a-2c）word教案
2015秋鲁教版英语八上Unit 2《Why don’t you talk to your parents》（SectionA Grammar-4c）word教案
2015秋鲁教版英语八上Unit 5《What’s the highest mountain in the world》（SectionA 3a-4c）word教案
2015秋鲁教版英语八上Unit 3《What were you doing when the rainstrom came》（SectionA Grammar-4c）word教案
2015秋鲁教版英语八上Unit 1《Could you please clean your room》（SectionA 3a-4c）word学案
2015秋鲁教版英语八上Unit 3《What were you doing when the rainstrom came》（SectionA 3a-3c）word学案
2015秋鲁教版英语八上Unit 3《What were you doing when the rainstrom came》（SectionA Grammar-4c）word学案
2015秋鲁教版英语八上Unit 2《Why don’t you talk to your parents》（SectionA 1a-2d）word教案
2015秋鲁教版英语八上Unit 3《What were you doing when the rainstrom came》（SectionB 1a-1d）word学案
鲁教版英语八上《Unit 6 How long have you been collecting shells》word教案
2015秋鲁教版英语八上Unit 4《An old man tried to move the mountains.》（SectionB 2b-3b）word教案
2015秋鲁教版英语八上Unit 5《What’s the highest mountain in the world》（SectionA 2a-2d）word教案
2015秋鲁教版英语八上Unit 5《What’s the highest mountain in the world》（SectionA 1a-1c）word教案
2015秋鲁教版英语八上Unit 2《Why don’t you talk to your parents》（SectionA 3a-3c）word学案
2015秋鲁教版英语八上Unit 1《Could you please clean your room》（SectionB 3a-Self check）word教案
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2015秋鲁教版英语八上Unit 3《What were you doing when the rainstrom came》（SectionA 1a-2d）word学案
2015秋鲁教版英语八上Unit 2《Why don’t you talk to your parents》（SectionB 3a-Self Check）word学案