as可作介詞、副詞、連詞和名詞四種詞性。中文含義有“像”、“作為”、“像……一樣”、“當(dāng)……時(shí)”、“隨著”、“因?yàn)椤?、“照……方式”、“阿斯”，還可以指“A”的復(fù)數(shù)。

as…as…意為"和……一樣"，表示同級(jí)的比較。使用時(shí)要注意第一個(gè)as為副詞，第二個(gè)as為連詞。其基本用法為as+ adj./ adv. +as…。例如：

This film is as interesting as that one (is).

這部電影和那部電影一樣有趣。

Your pen writes as smoothly as mine (does).

你的鋼筆書(shū)寫(xiě)起來(lái)和我的一樣流暢。

其否定式為not as/so +adj./ adv. +as…結(jié)構(gòu)。例如：

This dictionary is not as/so useful as you think it is.

這部字典不如你想象的那樣有用。

I didn"t catch as many as I had expected.

我抓到的不如我預(yù)想的那么多。

若有修飾成分，如twice, three times, half, a quarter等，則其必須置于第一個(gè)as之前，例如：

You are not half as clever as you think you are.

你可不象自己想象的那么聰明。

She isn't going out with a man who is twice as old as she.

她不打算和一個(gè)比她大一倍的人出去散步。