前缀 un-
汉： 前缀un-来源于盎格鲁-撒克逊语，在形容度词或副词前，意为“not”；在名词前，意为“lack of reverse of”。此外，用做“cause to be no longer degrade from the position of”等意思时，主要把名词转为动词，或表示与原动词意思相对或相反的行为。
英：
un- (1)
prefix of negation, Old English un-, from P.Gmc. *un- (cf. Old Frisian, Old High German, German un-, Gothic un-, Dutch on-), from PIE *n- (cf. Sanskrit a-, an- "not," Greek a-, an-, Old Irish an-, Latin in-), a variant of PIE root *ne- "not" (cf. Avestan na, Old Church Slavonic and Lithuanian ne "not," Latin ne "that not," Greek ne- "not," Old Irish ni, Cornish ny "not").
Freely and widely used since Old English in compounds with native and imported words, it disputes with Latin-derived cognate in- the right to form the negation of certain words (indigestable/undigestable, etc.). Often euphemistic (e.g. untruth for "lie"). The most prolific of English prefixes, it even is used to make words from phrases (e.g. uncalled-for, c.1600; undreamed-of, 1630s; uncome-at-able, 1690s; unputdownable, 1947, of a book; un-in-one-breath-utterable, Ben Jonson; etc.). As a prefix in telegram-ese to ｒｅｐｌａｃｅ not and save the cost of a word, it is first attested 1936.
un- (2)
prefix of reversal (e.g. unhand, undo, unbutton), O.E. on-, un-, from P.Gmc. *andi- (cf. O.S. ant-, O.N. and-, Du. ont-, O.H.G. ant-, Ger. ant-, Goth. and- "against"), from PIE *anti "facing opposite, near, in front of, before" (see ante).
共详细分为以下六类意思：
1、un-表示“不”
unabashed
a.not abashed,embarrassed or awed 不害怕的，不难为情，泰然的
Tim appeared unabashed by all the media attention
蒂姆成了媒体的焦点，却也满不在乎。
unalterable
a.not alterable 无法变更的 alter=other
The state of New York has designed its new drivers'licenses to be virtually.
纽约新设计的驾驶执照实际上是不可变更的。
2、un-表示“无”
uncouth
a.tough,awkward,not cultured (人，行为)粗鲁的，粗俗的；笨拙的；无教养的
A man considered uncouth or mean; a boor.
被认为粗鲁的或卑鄙的人; 举止粗鲁的人
3、un-表示“非”
unearthly
a.very strange;superntural and therefore frightening 非自然的；异常的；怪异的；
An unearthly glow emanated from the house.
那个房子里发出一束奇异的光。
4、un-表示“未”
unmitigated
a.not mitigated;complete;absolute 未减
轻的；完全的；绝对的 词根mitig=soft
The UN can no longer turn a blind eye to the unmitigated suffering of the Bosnians.
联合国再也不能对波斯尼亚人未曾减轻的痛苦坐视不管了。
5、un-表示“相反动作、取消、除去”
unlock
vt. 开启，显露，放开
I unlocked the door and went into the room.
我打开房门，然后走进屋里。
6、un-表示“由...中弄出”
untomb
v. 由坟墓中掘出，揭露
unearth
vt. 发掘，掘出，发现并披露
I unearthed the portrait from the attic.
我从阁楼上搜出这幅画像。
