习惯上用于“on+名词”的若干搭配
英语中习惯上用于“on +名词”的搭配不多，常见的有以下一些：
■on approval（指货物）供试用的；包退包换的
The goods were supplied on approval. 这些商品是供试用的。
Please send me the book on approval. 请将该书寄来一阅，以便决定购买与否。
【注】有时approval前可以有修饰语。如：
We have sent you these goods on five days’ approval. 我们送上这包包退商品，供君试用五天。
■on average 中等（水平）；平均起来，按平均数计算
His school work is on (the) average. 他的学业成绩属中等水平。
He smokes 10 cigarettes a day on average. 他平均每天抽10支烟。
We received 20 letters a day on average. 我们平均每天接到20封来信。
【注】有时也说 on an average或on the average。
■on board 在船上，在飞机上，在火车上
When everybody was on board, the ship sailed. 等所有的人都上了船，船启航了。
When all passengers were on board, the train pulled out of the station. 所有乘客都上车后，火车开出了车站。
【注】on board还可用作介词，其后跟表示车、船、飞机的名词。如：
He has never been on board a ship before. 他从来没有乘过船。
Mr Smith is on board one of those ships. 史密斯先生在其中的一条船上。
■on business 办事，因公
He went to
Are you here on business or for pleasure? 你来此地是出差还是游览？
■on condition 倘若，如果，条件是
I’ll come on condition John is invited too. 如果约翰也被邀请，我就来。
Visitors are allowed in the gardens on condition that they don’t touch the plants. 参观者允许进入花园，条件是不触摸这些植物。
【注】相当于连后，其后引导句子，可视为其后省略了that。
■on credit 赊欠
We don’t sell on credit. 我们不赊销。
If you don’t have enough cash, why don’t you make arrangements to buy the car on credit？ 假若你现金不够，为什么不作出安排，赊购这部汽车？
■on cue 恰好在这时候，就在这时候
He said she would be back very soon and, right on cue, she walked in. 他说她很快就回来，说着说着，她走进来了。
Just as we’re leaving, right on cue, the kids say they need the toilet. 不早不晚，就在我们要离开之时，孩子们说他们要上厕所。
■on demand 一经要求；在请求时
This check is payable on demand. 这是见票即付的支票。
Passengers must show their tickets on demand. 查票时旅客须出示车票。
■on display 被展示，被陈列
A collection of photographs was on display in the hall. 大厅里展出了一辑照片。
Treasures from the sunken ship were put on display at the museum. 沉船的财宝在博物馆展览。
■on duty 值日
Who’s on duty today? 今天谁值日？
They always have guards on duty at the door. 门口他们总是有门卫值班。
■on earth 在世上；到底
I am the luckiest man on earth. 我是世上最幸运的男人。
What on earth is the problem? 到底是什么问题？
■on edge 紧张不安，烦躁
She was a bit on edge till she heard he was safe. 她听到他安然无恙才放下心来。
I’m sorry if I rude to you- I’m a bit on edge at the moment.要是我冒犯了你，那么我很抱歉—我此刻有点烦躁。