obedience is the first duty of a soldier. 軍人以服從命令為天職。

　　observation is the best teacher.觀察是的老師。

　　offense is the best defense. 進(jìn)攻是的防御。

　　old friends and old wines are best. 陳酒味醇，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，兩次小。

　　once a thief, always a thief. 偷盜一次，做賊一世。

　　once bitten, twice shy. 一朝被蛇咬，十年怕井繩。

　　one boy is a boy, two boys half a boy, three boys no boy.　一個(gè)和尚挑水喝，兩個(gè)和尚抬水喝，三個(gè)和尚沒(méi)水喝。

　　one cannot put back the clock.時(shí)鐘不能倒轉(zhuǎn)。

　　one eyewitness is better than ten hearsays. 百聞不如一見(jiàn)。

　　one false move may lose the game. 一著不慎，滿盤皆輸。

　　one good turn deserves another. 行善積德。

　　one hour today is worth two tomorrow. 爭(zhēng)分奪秒效率高。

　　one man’s fault is other man’s lesson. 前車之鑒。

　　one never loses anything by politeness. 講禮貌不吃虧。

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

　　one’s words reflect one’s thinking. 言為心聲。

　　out of debt, out of danger.無(wú)債一身輕。

　　out of office, out of danger. 無(wú)官一身輕。

　　out of sight, out of mind. 眼不見(jiàn)，心為靜。