合成动词　　在英语的合成词（compound words）中，合成动词（compound verbs）的数目较少，主要有下面三种类别：

　　㈠副词+动词，如 outdo, overcome, undermine, upset, cross-question, withhold, backbite 等。

　　㈡名词+动词，如 sunbathe, sidetrack, typewrite, house-hunt, browbeat, hoodwink, waylay 等。

　　㈢形容词+动词，如 whitewash, safeguard, shortlist, blackmail 等。

　　这三类合成动词中，以第一种最为丰富，特别是那些由“over, under, out”引导的，更显得多彩多姿。

　　由 over 引导的合成动词含有“太多、过多”的意思，如： overact, overburden, overcharge, overdo, overdress, overeat, overestimate, overpower, overpraise, overproduce, overprotect, overrule, oversleep, overspend, overstate, overstay, overwork 等。

　　由 under 引导的合成动词含 有“太少、不足”的意思，如： undercharge, underpay, underrate, understate, undervalue, underwork 等。

　　由 out 引导的合成动词则含有“超过、胜过”之意，如： outdo, outgrow, outlive, outnumber, outside, outrank, outshine, outstay, outstrip, outweigh, outwit 等。

　　现在举些句子示范：
① The food cost $3, but he was overcharged by 50 cents.
② Some romantic scenes in our TV shows were overdone.
③ Don't overstate your predicament or people will not believe you.
④ Some reporters understated the seriousness of the regional financial turmoil.
⑤ The staff of the company felt that their contribution had been undervalued.
⑥ Chinese swimmers outdid their opponents.
⑦ This type of computer has outlived its usefulness.
⑧ The advantages of the new salary scheme far outweigh its disadvantages.

　　最后，必须注意的是：不是凡是“over ”就是“过多、太多” ，凡是“under”就是“太少、不足”或凡是“out”就是“超过、胜过”。反之，有些合成动词根本和这几个副词的意思风马牛不相及。例如：

　　● overhear（无意中听到）
　　● overlook（俯视、疏忽、忽略）
　　● oversee（监督）
　　● overshadow（使……暗然失色）
　　● overthrow（推翻）
　　● overturn（使翻覆）
　　● undergo（经历、遭受）
　　● underline（在……划线、强调）
　　● undermine（破坏）
　　● underpin（加强、巩固）
　　● understand（理解）
　　● understudy（充当替手）
　　● undertake（担任、着手）
　　● outline（略述）
　　● outrage（虐待，侵害）
　　● outspread（伸展）