onward
onward/ˈɔnwəd]/adj.&adv.向前（的）：the onward march of technological progress科技的向前发展；the onward march of history历史车轮滚滚向前They marched onward.他们向前前进。
opaque
opaque/əuˈpeik/adj.1.不透明的；不传热的：The once clear mountain stream is now polluted and opaque.曾经是很清澈的山溪,现在受到污染变得混浊了。2.难理解的，晦涩的：The report was w···
open/opener/opening
open/ˈəupən/ I.adj.1.开着的：The door is open.门开着。He stood there with mouth wide open.他张着大嘴站在那儿。2.开放的：an open letter公开信The road is open.那条路可通行。The un···
opera
opera/ˈɔpərə/n.［c］&［u］歌剧：opera house歌剧院，剧场；a light opera轻歌剧；a comic opera喜歌剧；be fond of opera喜欢歌剧An opera is a play set to music.歌剧是谱上曲的戏剧···
operate/operation/operational
operate/ˈɔpəreit/ I.vt.操作：It is very difficult to operate the machine.操作这台机器很难。The lift is operated by electricity.电梯是用电开动的。‖II.vi.1.动手术(on)：The doctor···
operative/operator
operative/ˈɔpərətiv,ˈɔpəreitiv/adj.(计划、法律等)实施中的，起作用的：operative section of a factory工厂的生产部门The scheme was fully operative by 2013.到2013年这一计划已完全···
opinion/opinionated
opinion/əˈpinjən/n.［c］&［u］意见，看法，主张：one’s political opinions政见，政治主张；public opinion舆论；an opinion about a matter (a person)对某事(某人)的意见；in one’···
opium
opium/ˈəupjəm/n. [u]鸦片：Opium-War鸦片战争(1839-1842)That man gave her a dose of opium.那男人给了她一剂鸦片。
opponent
opponent/əˈpəunənt/n.［c］对手，敌手；反对者（[反]proponent）：attack an opponent攻击对手；beat/defeat an opponent at an election在选举中击败对手；a bitter opponent死对头；an o···
opportunity
opportunity/ˌɔpəˈtju:niti/n.［c］&［u］机会，良机(= a good chance): equal opportunities均等的机会；at/on the first opportunity一有机会；afford/give an opportunity给予机会；···
