de-是个用法较为复杂的前缀。它原是个拉丁介副词，只出现在拉丁或法语借词中。de-依附在词根前，表示 down (from) 或away (from)的意思，有时则表示对词根的强调，有completely 的意思。 后来，de-被英语所同化，变成一个相当活跃的派生前缀。它可以加在动词或名词之前，生成带否定意义的动词。当它与动词结合时，基本意思是to undo,表示“做（与原动词）相反的动作”。当它与名词结合时，基本意思是to make down or away,表示“降低，剥离，取走”等动作。下面，我们按照de-的构词功能，分别予以介绍。

先观察由de-与词根结合的几个具有代表性的例子。

decline [ de- = down 下；clin = to bend 弯；-e=>“to bend down弯下去”→]v. ① bend or slope downwards 下倾 / The road declines at the turn.到拐弯处路转下坡了。② turn down; refuse 拒绝 / I have to decline your invitation because Mother is ill.妈妈病了，我只好谢绝你的邀请。

declination n. 倾斜；拒绝，谢绝

decrease [ de- = down 下;creas = to grow 变得；-e=>“ to grow downward 变得下降了”→] v. grow or become less 减少；减小/ Hunger decreases as one eats.吃东西时饥饿感就减少了。

debar [de- = away 外；bar = to shut 关=>“to shut away 把…关在外面”→]vt. shut out; prevent 排除；阻止 / He was debarred from club membership because of the scandal. 因为那件丑闻，他被俱乐部拒之门外。

detract [ de- = away 离；tract = to draw 抽=>“to draw away 抽离”→]v. take away a part; remove some value 减损；贬低 / The ugly frame detracts from the beauty of the picture. 难看的画框影响了这幅画的美丽。

detraction n. 减损；贬低