在英語的合成詞(compound words)中，合成動詞(compound verbs)的數目較少，主要有下面三種類別：

㈠副詞+動詞，如 outdo, overcome, undermine, upset, cross-question, withhold, backbite 等。

㈡名詞+動詞，如 sunbathe, sidetrack, typewrite, house-hunt, browbeat, hoodwink, waylay 等。

㈢形容詞+動詞，如 whitewash, safeguard, shortlist, blackmail 等。

這三類合成動詞中，以第一種最為豐富，特別是那些由“over, under, out”引導的，更顯得多彩多姿。

由 over 引導的合成動詞含有“太多、過多”的意思，如： overact, overburden, overcharge, overdo, overdress, overeat, overestimate, overpower, overpraise, overproduce, overprotect, overrule, oversleep, overspend, overstate, overstay, overwork 等。

由 under 引導的合成動詞含 有“太少、不足”的意思，如： undercharge, underpay, underrate, understate, undervalue, underwork 等。

由 out 引導的合成動詞則含有“超過、勝過”之意，如： outdo, outgrow, outlive, outnumber, outside, outrank, outshine, outstay, outstrip, outweigh, outwit 等。

現在舉些句子示范：

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，必須注意的是：不是凡是“over ”就是“過多、太多” ，凡是“under”就是“太少、不足”或凡是“out”就是“超過、勝過”。反之，有些合成動詞根本和這幾個副詞的意思風馬牛不相及。例如：

● overhear(無意中聽到)

● overlook(俯視、疏忽、忽略)

● oversee(監督)

● overshadow(使……暗然失色)

● overthrow(推翻)

● overturn(使翻覆)

● undergo(經歷、遭受)

● underline(在……劃線、強調)

● undermine(破壞)

● underpin(加強、鞏固)

● understand(理解)

● understudy(充當替手)

● undertake(擔任、著手)

● outline(略述)

● outrage(虐待，侵害)

● outspread(伸展)