Necessity is the mother of invention.
［注解］原句是“Art imitates Nature, and necessity is the mother of invention”。艺术模仿自然，需要为发明之母。
［译］需要是发明的动力。
Necessity knows no law.
［注解］这是做事不择手段的辩解语。necessity指迫不得已的需要。
［译］需要面前无法律。
Need makes the old wife trot.
［译］事急老妪跑。
Never buy a pig in a poke.
［译］东西没看清，不要急着买。
Never cackle till your egg is laid.
［注解］cackle鸡下蛋后的咯咯叫声。
［译］事未完成，莫先声张。
Never cross a bridge till you come to it.
［注解］古时的桥不像现代的桥这么结实，过河有危险，故产生此谚语。喻指Don't worry about future problems before you need to，不要杞人忧天，船到桥头自然直。美国诗人朗费罗曾说过这是一句古老而又极具智慧的谚语。
［译］还没到桥头，别为过桥愁；困难没出现，切莫先担忧。
Never do things by halves.
［注解］do things by halves事情做到半途而废，做事不彻底，做事草率不周。
［译］凡事不可半途而废；做事应有始有终。
Never hit a man when he's down.
［译］不要落井下石。
Never offer to teach fish to swim.
［译］切莫班门弄斧。
No answer is also answer.
［译］不回答也是一种回答。
Nobody's enemy but his own.
［译］自寻苦恼。