Nature is the true law.

　　天行有常，不为尧存，不为桀亡。

　　Necessity is the mother of invention.

　　需要是发明的动力。

　　Never fish in trouble water.

　　不要混水摸鱼。

　　Never judge from appearances.

　　不可以貌取人。

　　Never say die.

　　永不言败。

　　Never too old to learn, never too late to turn.

　　亡羊补牢，为时未晚。

　　New wine in old bottles.

　　旧瓶装新酒。

　　No cross, no crown.

　　不经历风雨，怎么见彩虹。

　　No garden without its weeds.

　　没有不长草的园子。

　　No living man all things can.

　　世上没有万事通。

　　No man can do two things at once.

　　一心不可二用。

　　No man is born wise or learned.

　　没有生而知之者。

　　No man is content.

　　人心不足蛇吞象。

　　No man is wise at all times.

　　聪明一世，糊涂一时。

　　None are so blind as those who won't see.

　　视而不见。

　　None are so deaf as those who won't hear.

　　充耳不闻。

　　No news is good news.

　　没有消息就是好消息。

　　No one can call back yesterday.

　　昨日不会重现。

　　No pains, no gains.

　　没有付出就没有收获。

　　No pleasure without pain.

　　没有苦就没有乐。

　　No rose without a thorn.

　　没有不带刺的玫瑰。

　　No sweet without sweat.

　　先苦后甜。

　　No smoke without fire.

　　无风不起浪。

　　Nothing brave, nothing have.

　　不入虎穴，焉得虎子。

　　Nothing dries sooner than a tear.

　　眼泪干得最快。

　　Nothing in the world is difficult for one who sets his mind to it.

　　世上无难事，只怕有心人。

　　Nothing is difficult to the man who will try.

　　世上无难事，只要肯登攀。

　　Nothing seek, nothing find.

　　没有追求就没有收获。

　　Nothing is so necessary for travelers as languages.

　　外出旅行，语言最要紧。

　　Nothing is to be got without pains but poverty.

　　世上唯有贫穷可以不劳而获。

　　Not to advance is to go back.

　　不进则退。

　　Not to know what happened before one was born is always to be a child.

　　不懂世故，幼稚可笑。

　　No way is impossible to courage.

　　勇者无惧。

　　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。

　　Offense is the best defense.

　　进攻是最好的防御。

　　Old friends and old wines are best.

　　陈酒味醇，老友情深。

　　Old sin makes new shame.

　　一失足成千古恨。

　　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 bitten, twice shy.

　　一朝被蛇咬，十年怕井绳。

　　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 cannot put back the clock.

　　时钟不能倒转。

　　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 good turn deserves another.

　　行善积德。

　　One hour today is worth two tomorrow.

　　争分夺秒效率高。

　　One man's fault is other man's lesson.

　　前车之鉴。

　　One never loses anything by politeness.

　　讲礼貌不吃亏。

　　One swallow does not make a summer.

　　一燕不成夏。

　　One's words reflect one's thinking.

　　言为心声。

　　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。