on /ɔn/ I. prep. 1.在…上：Put your book on the desk.把你的书放在课桌上。2.在…时候；和…同时： on New Year’s Day (Friday) 在元旦(星期五)；on (the morning of) July 1st 在7月1日(上午) 3. 在…后立即：［考句］On seeing the damage he had done, the child felt ashamed. 看到由他造成的损失，这小孩感到羞愧。3.［表示地点］在…里：My father worked on a farm.我父亲在农场工作过。 4.在…旁，沿着…：He sat on my right.他坐在我右边。There are trees on both sides of the street.街道两旁都是树。5.关于：This is a book on radio.这是一本关于无线电的书。(比较：a book about radio,指比较简单的科普读物)  6. 凭，靠，根据： On what ground?凭什么理由? based on fact 以事实为根据；act on principle 按原则办事 7. 处于…情况中； on fire 着火；on sale出售；on business出差 8.向，朝，针对(=toward): march on Paris 向巴黎前进 The house looks out on the sea.这座房屋可以眺望海洋。9. 是…成员： He is on the committee.他担任委员/他是一个委员。‖II.adv. 1.向前，(进行)下去；在发生中： We walked on without speaking.我们默默地向前走。The new play is on.新戏正在上演。2.放(穿、连结)上：have nothing on 一丝不挂 The radio is on. 无线电开着。3.用于习语 on and on 不断地，持续地：The road seemed to go on and on. 这条路好像没有尽头。The band played on and on, repeating the same tunes.乐队一直在不停地重复同一个旋律。and so on 等等，诸如此类：We have to study Chinese, maths, English, physics and so on. 我们必须学习语文、数学、英语、物理等科目。