英语前缀对于单词的扩展非常重要，同时也是猜测词意的重要方法。

下面列举一些常见的前缀的含义

re-, pre-, pro-, in-, un-, mis-，dis-,dys-,de-

1) re = again 再一次

reheat (heat again)重新加热

reuse (use again)重新使用

replay (play again)重新播放

play the video播放视频

revise (look at again) vt.复习;修订(再看一遍不是为了复习就是修改错误的地方)

（词根 vis=看）

He was revising what he has written.他正在修改他所写的东西。

2) pre = before, already 在...之前

precooked (cooked already) vt.预煮，预先烹调

prepacked (packed already)

prewar (before a war)

3) pro = in support of, in favour of (often followed by a hyphen) 赞同；亲...，拥护；

proactive (in favour of being active)

pro-British (in favour of Britain) 亲英

pro-capitalist (in favour of capitalism) 亲资

4) un = not 否定

unclean (not clean),

unhygienic (not hygienic),

unhappy (not happy)

5) in = not 否定（前缀in有很多种含义，这里只了解最常见含义）

incomplete (not complete)

intolerant (not tolerant)

inaccurate (not accurate)

6) mis = wrong, or not 错误/否定

mishear (to hear incorrectly),

misunderstanding (a situation when people understand each other wrongly),

mislead (to make someone believe the wrong thing)

7）dis- usually gives the opposite meaning.

disagree （ the opposite of agree）

disappear （ the opposite of appear）

discomfort （ the opposite of comfort）

8)dys- are usually medical. (dys通常跟医学的专有名词有关)

注意：后缀-ia通常表示...疾病

dyskinesia (difficulty moving normally)运动障碍

knee膝盖

dysphagia (difficulty swallowing) 吞咽困难

dyssomnia (difficulty sleeping) 睡眠障碍

9）De- away/not

1.often has the idea of moving 'away' from something. 远离...

2.Or, like dis-, it can also give an opposite meaning. 否定（not）

decentralise is to move things away from the centre (the opposite of centralise).

If you deforest land, you take the trees away.

And to detox is to remove toxins (harmful substances).

toxic a.有毒的

toxin n. 毒素