名人教英文：preposition 介系字
prepositions are the most frequently used words in the english language. yet, they are the most difficult. this is because their usage is often governed by convention, rather than by hard and fast rules. once wrongly used, the preposition changes the meaning of a sentence altogether.
介系字是最常用、也是最难用的英文字。这是因为它的用法往往是跟习俗而不是跟严厉之规则，一旦用错，整句的意思也变了。
a preposition governs the relationship between its object and the words that come before it. it acts as an adjunct, the right choice of which gives an adjective, noun or verb more grammatical versatility.
介系字是用来支配其受事者与其前辞之关系。如同修饰语，可令其形容词、名词或动词在文法上多元化。
prepositions work with :
1. adjective
e.g. i am grateful for your help.
2. noun
e.g. the weather in hong kong is humid.
3. verb
a) to show different meanings of the same verb:
e.g. i look for my lost book. 我找寻遗失的书。
e.g. i will look into it. 我会注意此事。
e.g. look out! 小心﹗
b) certain prepositions must be used with certain verbs. 某些介系字必须跟某些动词一齐用︰
e.g. this book belongs to me. 这本书是我的。
e.g. this class consists of boys only.
这班只有男孩子。
e.g. carry on! 继续吧﹗
c) different prepositions increase a verb's grammatical versatility. 不同的介系字可令某动词变化良多︰
e.g. i look sad without you.
没有你，我样子悲哀。
verb + adj. + prep. + pronoun
e.g. i look forward to seeing you.
我盼望着见你。
verb + adverb + prep. + gerund
e.g. i am looked over by my boss.
我被上司忽略。
verb+ prep. "over by" + object of prep. "boss"
simple prepositions
e.g. above, about, after, against, at, as, below, by, for, from, in,
on, of, to, etc.
complex prepositions
e.g. in spite of, in respect of, over by, with respect to, in accordance with, etc.
prepositions also may overlap with other categories. 介系字可与其他类别重迭。
a) adverbs 助动词
e.g. preposition: i am down in the dumps. 我好沮丧。
e.g. adverb: i walk down. 我往下走。
b) conjunctions 连接词
e.g. preposition: i put the book before me. 我把书放在我前面。
e.g. conjunction: before i met you, i was very sad. 在我没见你之前，我很忧愁。
revision
fill in the blanks with an appropriate preposition.
1. i look ______ him. 我敬佩他。
2. ____________ your request, i support you. 我支持你的申请书。
3. ____________ your effort, you have still failed. 尽管你努力，你还是失败了。
4. ____________ your effort, you have succeeded. 因为你努力，你成功了。
5. i am ______ this policy. 我反对此政策。