1.The water that bears the boat is the same that swallows it up.水能载舟，亦能覆舟。

2.Observation is the best teacher.观察是最好的老师。

3.Offense¹ is the best defense².进攻是最好的防御。

4.Old friends and old wines are the best.陈酒味醇，老友情深。

5.Old sin makes new shame.一失足成千古恨。

6.Once a man and twice a child.一次老，两次小。

7.Once a thief, always a thief.偷盗一次，做贼一世。

8.Once bitten, wice shy.一朝被蛇咬，十年怕井绳。

9.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。

10.Wet behind the ears.乳臭未干。

11.One cannot put back the clock.时钟不能倒转。

12.One eyewitness³ is better than ten hearsays.百闻不如一见。

13.One false move may lose the game.一着不慎，满盘皆输。

14.One good turn deserves another.行善积德。

15.One hour today is worth two tomorrow.争分夺秒效率高。

16.One man‘s fault is other man’s lesson.前车之鉴。

17.One never loses anything by politeness.讲礼貌不吃亏。

18.One swallow does not make a summer.一燕不成夏。

19.One‘s words reflect one’s thinking.言为心声。

20.Out of debt, out of danger.无债一身轻。

21.Out of office, out of danger.无官一身轻。

22.Out of sight, out of mind.眼不见，心为静。

23.Patience is the best remedy.忍耐是良药。

24.Penny wise, pound foolish.贪小便宜吃大亏。

25.Please the eye and plague the heart. 贪图一时快活，必然留下隐祸。

26.Pleasure comes through toil⁴.苦尽甘来。

27.Pour water into a sieve⁵.竹篮子打水一场空。

28.Practice makes perfect.熟能生巧。

29.Praise is not pudding.恭维话不能当饭吃。

30.Praise makes good men better, and bad men worse.好人越夸越好，坏人越夸越糟。