Oaks may fall when reeds stand the storm. 树大招风。
Obedience is the first duty of a soldier. 军人以服从命令为天职。
Observation is the best teacher. 观察是最好的老师。
Of all the possessions of this life fame is the noblest; when the body has sunk into the dust the great name still lives. 人生最可宝贵的是声誉，躯体入土后，声誉犹存。
Of earthly goods the best is a good wife. A bad the bitterest curse of human life。
Of nothing comes nothing. 无中不聀?璀?有。
Of two evils choose the least. 权衡两害，取其轻者。
Of young men die many, of old men escape not any. 年轻人死得不少，而年迈者是在劫难逃。
Offence is the best defence. 进攻是最好的防御。
Offense is the best defense. 进攻是最好的防御。
Often and little eating makes a man fat. 少吃多餐，身强体胖。
Old bees yield no honey. 老蜂不酿蜜。
Old birds are not caught with new nests. 新巢捉不到老鸟。
Old birds are not to be caught with shaff. 老谋是不会失算的。
Old foxes want no tutors. 老狐狸不需要教师。
Old friends and old wine are best. 古交友情深，陈酒香味醇。
Old friends and old wines are best. 陈酒味醇，老友情深。
Old love will not be forgotten. 旧情永难忘。
Old sin makes new shame. 一失足成千古恨。
Old vessels must leak. 旧船必漏。
Old wood best to burn, old wine to drink, old friends to trust, and old authors to read. 老柴最好烧，陈酒最好饮，老友最可靠，老作家的书最好读。
Old wood is best to burn, old book to read. 老柴好烧，老书宜读。
Old wood is best to burn, old horse to ride. 老柴好烧，老马好骑。
Older and wiser. 越老越聪明。
Omelets are not made without breaking eggs. 有失才有得。
On the choice of friends. Our good or evil name depends。
On the great clock of time there is but one word, “”Now. ” 在伟大的时钟上，只有一个词，就是“现在”。
Once a beggar, always a beggar. 一次做乞丐，永远是乞丐。
Once a devil, always a devil. 一次做魔鬼，永远是魔鬼。
Once a knave, ever a knave. 一朝失足，铸成千古恨。
Once a man and twice a child. 一次老，两次小。
Once a thief, always a thief. 偷盗一次，做贼一世。
Once bit, twice shy. 一朝被蛇咬，三年怕草绳。
Once bitten, twice shy. 一朝被蛇咬，十年怕井绳。
Once is no custom. 一次不成例。
Once on shore, we pray no more. 一旦上了岸，就不再祈祷。
One barking dog sets all street a-barking. 一狗吠声响，狗吠满街坊。
One beats the bush, and another catches the birds. 坐享其成。
One boy is a boy, two boys half a boy, three boys no boy. 一个和尚挑水喝，两个和尚抬水喝，三个和尚没水喝。
One boy is more trouble than a dozen girls. 一个男孩比十二个女孩还要麻烦。
One cannot always be a hero, but one can always be a man. 人难一世称雄，但可一生为人。
One cannot do a foolish thing once in one’s life, but one must hear of it a hundred times. 为人一生一件蠢事也不做，但要听到上百遍蠢事。
One cannot eat one’s cake and have it. 事难两全其美。
One cannot get blood from a stone. 石头里抽不出血。
One cannot make a silk purse out of a sow’s ear. 朽木不可雕。
One cannot make bricks without straw. 巧妇难为无米之炊。
One cannot put back the clock. 时钟不能倒转。
One chick keeps a hen busy. 一只小鸡已够母鸡辛忙。
One cloud is enough to eclipse all the sun. 一叶可障目。
One crowded hour of glorious life is worth an age without a name. 光辉生活中忙迫的一个小时抵得上无为的一世。
One drop of poison infects the whole tun of wine. 一滴之毒，毒染整桶之酒。
One enemy can do more hurt than ten friends can do good. 十个朋友做的好事抵不上一个敌人造成的危害。
One enemy is too much. 一个敌人也太多。
One eyewitness is better than ten hearsays. 百闻不如一见。
One false move may lose the game. 一着不慎，满盘皆输。
One false step will make a great difference. 失之毫厘，谬以千里。
One father can support ten children, ten children cannot support one father. 一个父亲能扶养十个孩子，十个孩子却不能赡养一个父亲。
One father is more than a hundred schoolmasters. 一个父亲胜于一百个教师。
One flower makes no garland. 一木不能成林。
One foe is too many; and a hundred friends too few. 朋友成百犹觉少，仇敌一人已嫌多。
One fool makes many. 一人傻，傻大家。
One foot is better than two crutches. 一只脚胜过两根拐杖。
One good head is better than a hundred strong hands. 上百双有力的手，不如一个聪明的头脑。
One good mother is worth a hundred schoolmasters. 一个好的母亲顶得上一百个教师。
One good turn deserves another. 行善积德。
One half of the world does not know how the other half lives. 贫富不相知。
One has lived too near a wood to be frightened by owls. 深知底蕴，不以为怪。
One honest word is better than two oaths. 两句誓言不如一句实话。
One hour today is worth two tomorrow. 争分夺秒效率高。
One hour’s sleep before midnight is worth three after. 午夜前睡一小时抵得上午夜后睡三小时。
One is never too old to learn. 人没有老得不能学的时候。
One love drives out another. 新爱逐旧欢。
One man makes a chair and another man sits in it. 坐享其成。
One man may steal a horse while another may not look over a hedge. 只许州官放火，不许百姓点灯。
One man, no man. 个人是渺小的。
One man’s fault is another man’s lesson. 一个人的过失是另一个人的教训。
One man’s fault is other man’s lesson. 前车之鉴。
One man’s meat is another man’s poison. 一个人的美点，可是另一人的毒药。
One may sooner fall than rise. 跌倒容易爬起难。
One may think that dares not speak. 人可思其不敢言者。
One misfortune comes on the neck of another. 祸不单行。
One must draw the line somewhere. 人之所为，总有限度。
One must drink as one brews. 自作自受。
One must howl with the wolves. 入乡随俗。
One never loses anything by politeness. 讲礼貌不吃亏。
One never loses by doing a good turn. 行善者决无一失。
One penny witgh right is better than a thousand without right. 合法得来一个钱，胜过非法钱一千。
One ploughs, another sow; who will reap no one knows. 有的耕，有的播，谁来收获很难说。
One rotten apple spoils the whole barrel. 一只烂苹果烂一萝苹果。
One should eat to live, not live to eat. 人为生而食，非为食而生。
One sin opens the door for another. 一个罪恶常为另一个罪恶开门。
One sows another reaps. 不劳而获。
One swallow does not make a summ. 一燕不成夏。
One swallow does not make a summer. 一燕不成夏。
One thorn of experience is worth a whole wilderness of warning. 一次痛苦的经验抵得上千百次的告诫。
One today is worth two tomorrow. 把握住今天胜过两个明天。
One today is worth two tomorrows. 一个今天胜似两个明天。
One who can do everything can do nothing. 什麽都能做，什麽都不行。
One woe doth tread upon another’s heels. 祸不单行。
One wrong (or false) move can lose the whole game. 棋错一著，全盘皆输。
One wrong thought may cause a lifelong regret. 一念之错可铸终生之恨。
One’s mantle falls on somebody. 春风化雨。
One’s sin will find one out. 坏事终归要败露。
One’s words reflect one’s thinking. 言为心声。
Only that which is honestly got is gain. 正当的收入才是真正的收入。
Only they who fulfill their duty in everday matters will fulfill them on great occasions. 只有在日常事务上尽责的人，才能在重大事情上尽责。
Open confession is good for the soul. 坦白交代，身心愉快。
Open not your door when the devil knocks. 不要受人的诱惑。
Opportunity knock at the door only once. 机不可失。
Opportunity makes the thief. 疏忽招盗贼。
Opportunity, sooner or later, comes to all who work and wish. 只要努力工作而有志向，机会迟早终会来临。
Other men live to eat, while I eat to live. 别人为食而生活，我为生活而食。
Our affections are our life. – We live by them; they supply our warmth。
Our best friends are they who tell us our faults and help us to mend them. 最好的朋友是指出我们的缺点并帮助改正的人。
Our bravest and best lessons are not learnt through success, but through misadventure. 最美好的教训不是得之于成功，而是来之于不幸。
Our greatest glory consists not in never falling, but in rising every time we fall. 我们最大的光荣并不在于永不跌倒，而在于每次跌倒后能起来。
Our happiness consists not in killing others, but in sacrificing ourselves for others. 我们最大幸福并不是杀害别人，而是为别人而牺牲自己。
Our own actions are our security, not others’ judgements. 我们的行为是自己的保证而不是别人的鉴定。
Our sweetest songs are those that tell of saddest thought. 最甜美的的歌是诉说最悲伤的哀思。
Out of debt, out of danger. 无债一身轻。
Out of office, out of danger. 无官一身轻。
Out of sight, out of mind. 眼不见，心为静。
Overdone is worse than undone. 过犹不及。