ultraviolet
adj. with a wavelengh that is just beyond the violet end of the visible spectrum（指辐射）紫外的 of or using such radiation 紫外线的；利用紫外线的。
ultraviolet rays， 紫外线 /an ultraviolet lamp 紫外线灯。
In any event， you should choose a reputable manufacturer. Whatever product you use should emit only visible light， because ultraviolet light damages the eyes.
不管怎样，你应该选择名牌产品。而且无论你使用哪一种产品，它们都应该只放射可见光，因为紫外线会对眼睛造成损伤。(2005年6月阅读理解)。
unanimous
adj. all agreeing on a decision or an opinion 一致同意的，无异议的。
The proposal was accepted with unanimous approval.
全体一致通过了该项协议。
underestimate
v. to make too low an estimate of sb./sth. 低估，看轻。
You shouldn t underestimate your opponent.
你不应该低估对手。
undermine
v. weaken or destroy by stages 逐渐削弱，暗中破坏。
A series of wrongful convictions has undermined public confidence in the police and the courts.
一系列错误的宣判削弱了公众对警方和法庭的信心。
unemployment
n. state of being employment 失业，失业状况 amount of unused labor 失业人数。
Concerned about the rising level of unemployment， the government is striving to create more new jobs.
政府对不断上升的失业率深为关切，因此正在努力设法创造更多新的就业机会。
unfold
v. to open from a folded position 展开，打开，摊开。
The garden chair unfolds to make a campbed.
花园中的这把椅子可以打开当行军床用。
unify
v. form sth. into a single unit make uniform 使成为一体，使一致。
They were unified into one nation.
他们统一为一个国家。
update
v. bring (sth.) up to date， modernize （更新，使现代化） give sb. the latest information (about sth.) 提供最新信息。
Can you give me an update on any policy changes since we last spoke？
你能不能给我提供我们上次谈话以来政策变化的最新消息？
upgrade
v. raise sb./sth. to a higher grade or rank 提升级别。
The consulate was upgraded to embassy status.
该领事馆已升格为大使馆。