介词是英语中最活跃的词类之一。许多介词搭配力特别强，和其他词连用可以表示各种不同的意思。大部分的习用语，都是由介词和其他词构成的。翻开一页书，我们可以找到大量介词。因此掌握好介词是学好英语的关键之一。英语中最常用的介词有下面这些，可分为三类：
1.简单介词:
about, across, after, against, among, around, at, before, behind, below, beside, besides, between, beyond, but, by, despite, down, during, except, for, from, in, like, of, off, on, over, near, past, round, since, though, till, to, forward (s), under, until, up, with, per, via.
2.合成介词:
in side, into, onto, out of, throughout, outside, upon, within, without.
3.成语介词:
according to，along with，apart from，as for，as to，because of，by mean of，in front of，in spite of，instead of，in accordance with，on account of，on behalf of，due to，owing to，together with，up to，with regard to，next to，prior to等。
其中最重要的是简单介词。成语介词和介词的成语的区分并不很明显。大体上说来，意思上和作用上相当于一个介词的，就可称为成语介词，如：in front of接近before，in addition to接近besides，in spite of 接近 despite.
