6104.unconscious(形)無意識的
反義詞conscious
I was unconscious of her presence．
我不知道她在場。

6105.unconsciously(副)無意識地
Perhaps,unconsciously, I've done something to offend her．
我也許無意中做了什么得罪她的事。

6106.underdeveloped(形)發育不全的
反義詞developed
They voted aid for the underdeveloped countries in Asia.
他投票建議援助亞洲的不發達國家。

6107.underestimate(動)低估
反義詞overestimate
Those who underestimate the intelligence of the rivals will come to grief.
低估對手智慧的人會大吃苦頭的。

6108.undergo(動)經歷；接受
不規則變化underwent，undergone
My mother underwent major surgery last year．
我母親去年動過大手術。

6109.undergraduate(名)大學生；大學肄業生
She read histoy as an undergraduate.
她在大學攻讀歷史。

6110.undermine(動)在無形中損壞；削弱……的基礎
Streams undermine the rocks.
流水侵蝕巖石的基部。

6111.underneath(介)在……下面
The coin rolled underneath the piano．
硬幣滾到了鋼琴底下。

6112.undertake(動)承擔；保證
不規則變化undertook，undertaken
He undertook to pay the money back within six months．
他保證六個月內還錢。

6113.underworld(名)下層社會；黑社會
The police has informer in the London underworld.
警察在倫敦的下流社會中有告密者。

6114.undoubtedly(副)無疑地
There is undoubtedly a great deal of truth in what he says.
他所說的的確太部分都是實情。

6115.undress(動)脫下
She undressed and got into bed．
她解衣上床了。

6116.undue(形)過度的、過分的
同義詞excessive
They are taking undue advantage of the situation.
他們過分利用了這種情勢。

6117.uneasy(形)不當的、不舒服的
同義詞anxious
I am uneasy in my mind about the future．
我為前途擔憂。

6118.unemployed(形)失業的
How long have you been unemployed?
你失業多久了？

6119.unemployment(名)失業；失業人數
Unemployment hurts every person the country, not just those who have lost their jobs.
失業對國內的每一個人都有害，而不僅是那些丟飯碗的人。

6120.unexpected(形)意外的
同義詞suffer
I'm afraid the unexpected accident may botch up the dinner today.
恐怕這意想不到的事故會把今天的晚宴搞糟。

6121.unexpectedly(副)意外地、未料到地
They had arrived unexpectedly.
他們意外地到達了。

6122.unforgettable(形)難忘的
The war has branded an unforgettable lesson on our minds．
戰爭在我們心上烙下了永生難忘的教訓。

6123.unfortunate(形)不幸的
反義詞fortunate
He was unfortunate to lose in the final round,
他不幸在最后一輪輸了。

6124.unfortunately(副)不幸地
She had left for work unfortunately.
遺憾的是她已上班去了。

6125.unify(動)統一
In my opinion, Abraham Lincoln was honored mostly in the US because he unified the country.
在我看來，美國人敬重林肯，主要是因為他保持了美國的統一。

6126.union(名)工會；結合
In union there is strength.
團結就是力量。

6127.universal(形)全世界的；全盤的
The government introduced universal secondary education years ago.
幾年前，政府就倡導普及中等教育。

6128.universe(名)宇宙
They thought the earth was the center of the universe.
他們認為地球是宇宙的中心。

6129.unknown(形)未知的(名)無名之士
(形):The idtentity of the bombers remained unknown．
這些轟炸機的來路依然不明。
(名):The author had been an unknown.
這個作家一直默默無聞。

6130.unlimited(形)無限的
反義詞limited
Some of us have known for many, many years that the freedoms under the First Amendment are not totally unlimited.
我們有些人多年以來一直知道第一修正案授予的自由并不是完全沒有限制的。

6131.unload(動)從……卸下
Everyone helped unload the luggage from the car.
大家都幫著從汽車上卸行李。

6132.unlock(動)打開鎖、開啟
How can we unlock all the secrets of nature?
我們怎樣才能揭示大自然的全部奧秘呢？

6133.unnecessary(形)不必要的
反義詞necessary
They were found guilty af causing unnecessary suffering to animals.
他們因虐待動物而被判有罪。

6134.unofficial(形)非正式的
同義詞unlawful
Unofficial estimates put the figure at over2 million．
非官方的估計數字為200萬以上。

6135.unpleasant(形)令人不愉快的
The minerals in the water made it unpleasant to drink.
水里的礦物質使得這水挺難喝的。