on trial . on probation试验；试用

The new clerk was found on trial to be incompetent．这个新职员试用后被发现不合格。

You may take it on trial；if you like it，then buy it ．你可以把它拿去试用，要是你喜欢，就买下来。

on trial . in a court of law受审

John White was on trial for murder．约翰·怀特因谋杀罪受审。

on trust . without proof or close examination不加深究地

I took all he said on trust，for I thought he was telling the truth．他说的我都相信，因为我认为他是在讲真话。

on trust . in credit赊帐

We have known the family for years and you may safely supply the goods on trust．我们认识这一家已有多年了，你可以放心地赊销商品。

on view . showing publicly展览；供人观赏

Have you seen the photo placed on view? 你看过那张供人观赏的照片吗?

once for all . once and for all . definitely断然地

The mosquitoes must be destroyed once and for all．必须把这些蚊子全部消灭掉。

I'm going to settle this matter once and for all．我要彻底解决这个问题。

Once and for all，I'll not go swimming with you．我绝对不会同你一块去游泳。

once for all . once and for all . permanently水远地；一劳永逸地

The two countries decided to end the war once and for all．两国决定这场战争从此结束。

This is not something that can be completed once for all．这不是件可以一劳永逸的事。

once in a while . occasionally；now and then有时；偶尔

We go for a picnic in the park once in a while．我们有时去公园里野餐。

Once in a while the puppy would run away．小狗有时也会溜出去。

once more . a second time再度

He asked the question once more．他再次提出这个问题。

He said he would try once more．他说他将再试一次。

 once upon a time . long ago从前；很久以前

Once upon a time there dwelt a fisherman on the lakeside．从前湖边住着一个渔民。

Once upon a time there lived a king who had an ugly daughter．从前有一位国王，他有一个丑陋的女儿。

 once upon a time . sometime before now以前

Once upon a time she was thought to be the most talented actress in the country．以前她被认为是该国最有才华的女演员。

one after another . one after the other . one by one一个接一个

The wounded soldiers died one after another．伤兵相继死亡。

Two happy events came one after the other．两件喜事接踵而至。

one and all . everyone个个都；全都

One and all，from the cities and from the villages，came to see him off．城乡人民个个都来给他送行。

They took part in the National Day celebrations，one and all．他们全都参加了国庆节庆祝活动。

one and the same . the very same同一个；完全一样

One and the same idea occurred to each of them．他们每个人都想起同样的念头。

Dr．Jekyll and Mr．Hyde were one and the same person．吉基尔博士和海德先生是同一个人。

one another . each other彼此

They gave presents to one another at Christmas．圣诞节他们互赠礼品。

one by one . singly一个一个地；依次地

The students went into the classroom one by one．学生一个一个地走进教室。

one day . on a certain day（过去或将来的）某一天

I'll take you there one day．总有一天我会带你去那儿的。

He came to see me one day．有一天他来看过我。

one in a thousand . very good indeed千中之一；难得的人（或物）

Tom，not one in a thousand would have forgiven you as he has done．汤姆，很少有人会象他那样原谅你的。

She's one in a thousand．She does her work quickly and conscientiously and can always be relied on．她这个人是很难得的，干活利索认真，又总是那么可信赖。

only that . with the exception that除了；只是

He is a good student，only that he is a little lazy．他是个好学生，只是稍微懒一点。

only that . were it not that若不是；要是没有

I should like to go，only that I am ill．要是没病，我倒是很想去的。

I would come only that I'm engaged to dine out．若不是有约外出吃饭，我倒是愿意来的。

only too . very非常

I am only too glad to hear it ．我听了不胜欢喜。

He was only too willing to accept the proposal．他非常愿意接受那个建议。

open its doors . allow somebody or something to enter or join开门接纳；开放

That college was started for women only，but a few years ago，it opened its doors to men．那所学校原先只收女生，数年后兼收男生。

The art exhibition has opened its doors to both professional and amateur artists．艺术展览馆对专业的和业余的艺术工作者开放。

open its doors . begin doing business开张；开门

The new department store opened its doors last week．那家新百货商店上星期刚开张。