An old dog cannot alter its way of barking. 老狗难改吠声。

　　An old dog will learn no new tricks. 老家夥学不出新名堂。

　　An old physician, and a young lawyer. 医生年老的好，律师年轻的俏。

　　An old poacher makes the best keeper. 老偷猎者是最好的看守人。

　　An open door may tempt a saint. 一扇开著的大门可诱惑一个圣徒。

　　An optimist sees an opportunity in every calamity; a pessimist sees a calamity in every opportunity. 乐观的人在灾难中看到希望;悲观的人在希望中看到灾难。

　　An ounce of prevention is worth a pound of cure. 预防胜于治疗。

　　An ox is taken by the horns, and the man by the tongue. 牛因有脚而被抓，人因有舌而遭殃。

　　Answer a fool according to his folly. 以其人之道，还治其人之身。

　　An upright judge has more regard to justice than to men. 正直的法官重法胜于重人。

　　A penny saved is a penny earned(or gained). 省钱就是赚钱。

　　A pet lamb makes a cross ram. 宠坏的小羊将成为脾气坏的大羊。

　　A poor man who takes a rich wife has a ruler, not a wife. 穷汉娶富妻，必受老婆欺。

　　Apothecaries would not sugar their pills unless they were bitter. 好药不苦不会加糖衣。

　　Apparel makes the man. 马靠鞍装，人靠衣装。

　　Appearances are deceitful. 人不可貌相，海水不可斗量。

　　Appetite comes with eating. 食欲越吃越旺。

　　A quiet conscience sleeps in thunder. 白日不做亏心事，夜半不怕鬼敲门。

　　A ragged coat may cover an honest man. 不能以衣著取人。

　　Art is long, but lift is short. 人生有涯，而学无涯。