Obedience is the first duty of a soldier. 服从是军人的第一职责。
Observation is the best teacher. 观察为良师。
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. 贤妻最可贵，恶妇是灾星。
Offence is the best defence. 进攻是最好的防御。
Of nothing comes nothing. 无中不能生有。
Often and little eating makes a man fat. 少吃多餐，身强体胖。
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。
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 shaft. 老谋是不会失算的。
Older and wiser. 越老越聪明。
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 love will not be forgotten. 旧情永难忘。
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。
O liberty, how many crimes have been committed in thy name! 自由啊！假你的名义犯了多少罪啊！
Omelets are not made without breaking eggs. 有失才有得。
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. 一次为成人，两度当小孩。
Once bit, twice shy. 一朝被蛇咬，三年怕草绳。
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。
On earth there is nothing great but man, in man there is nothing great but mind. 在世界上没有一件东西有如人那样伟大，在人之内没有一件东西有如人心那么伟大。
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 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 be in two place at once.
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。