求翻译：介词通常放在名词或代词之前，他不能单独充当句子的成分，而必须跟其他的词连在一起，构成介词短语，才能在句子中起作用。Before在……以前。After在……以后。介词是什么意思？

The preposition usually placed before the noun or pronoun, he alone can not act as the composition of the sentence, must be followed by the other words together, constitute a prepositional phrase, can play a role in the sentence. before in ...... before. after ...... later. Preposition

A section is usually placed in noun phrase or word generation before, and he alone could not serve as a sentence, and must be followed by other words in between words, phrases, which can be played a role in the sentence. In previous Before . ... In After ... later. prepositions

The preposition usually places in front of the noun or the pronoun, he cannot alone act as the sentence the ingredient, but must with other words in the same place, the constitution preposition phrase, be able to have an effect continually in the sentence.Before in ......Before.After in ......Later.

Prepositions are usually placed before the noun or pronoun that he alone cannot serve as a component of the sentence, which must be followed by other words linked together, constitute a prepositional phrase, to function in a sentence. Before ... ... Before. After ... ... Later. Prepositions

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