英语里的定冠词、介词、副词、从句之类的我总是弄不明白，该怎么办？

(1)冠词分为不定冠词"a，an"、定冠词"the"和零冠词三种，零冠词指的是不用冠词的情况。

不定冠词表示泛指，定冠词表示特指。
(2)介词有on in about, above, across, after, against, among, at, before, behind, below, beneath, beside, besides, beyond, but, by, down, during, except, for, from, in, like, near, of, off, on, over, past, round, since, through, to towards, under, until, till, up, with inside, into, onto, outside, through

http://zhidao.baidu.com/question/36808184.html?si=1这里就是讲解介词的
http://zhidao.baidu.com/question/24920751.html?si=1

这里有很多介绍的,你可以看看