介词用来表明名词、代词与句中其它词的关系的词叫做介词。（是虚词，不能重读，不做单独做句子成份）根据构成形式分，简单介词由一个词构成，如at, on, in, after, before, behind等；合成介词由两个词合成在一起，如inside, outside, into, without, nearby等；双重介词由两个简单介词重叠在一起，如from behind, until after, from among等；短语介词由一个或几个简单介词和一个或几个其它词组合而成，如at the back of, instead of, in place of, in front of, at the top of等；动词－ing形式介词，如including, considering, regarding, concerning等。

介词可以根据意义分类。表示空间关系的有on, under, in, outside, in front of, behind, round, around, by等；表示时间的有at, off, throughout, underneath, as, between, since, until, during, till, for, before, after, from…to…, across, up, over, past等；表示方位的有beyond, opposite, onto, into, towards, through, against, along等；表示手段、施动者等的有like, in, by, with等；表示其它含义的有without, with, except, beside, of, another, instead of, plus, minus, like, unlike, but, from, according to, of course, per, about等。

连词用来连接单词、短语或句子的一种虚词，在句子中不单独作任何成份，一般不重读。连词可以根据构成成分分，简单连词包括and, or, but, if, because, so等；关联连词包括both…and, not only…but also…, not…but…等。

连词还可以按性质分类。并列连词包括and, or, but, for, while, when, however, as, nor等；从属连词包括whether, though, until, after, although, when, since, unless, because, before, that, if, when, as though, as if, even though, as long as, even if, so, than, whenever, wherever, which等。

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