on even terms . on even terms with . at the same level  . at the same level with （与…）不相上下

They are on even terms．他们不相上下。

on faith . without question or proof毫无疑问；无需证据

He looked so honest that we accepted his story on faith．他看上去极为诚实，我们也就毫不怀疑地相信了他的话。

on file . stored in a file存档

This card should be kept on file for reference．这张卡片应该存档以备参考。

Our documents on file may throw some light on the matter．我们保存的文件也许会对这件事有所启示。

on fire . burning着火；失火

We saw a house on fire when we passed the road．我们经过这条路时，看到一所房子失火了。

on fire . in a rage愤怒；急切

They were on fire with zeal to defend their native land．他们热血沸腾，决心捍卫自己的祖国。

He was on fire to rejoin his family after an absence of five years．他急切地想和阔别五年的家人团聚。

 on foot .  by walking步行

Sally's bicycle broke and she had to return home on foot．萨莉的自行车坏了，她只好步行回家。

 on foot .   being planned在计划中

Plans have been set on foot by the company for a party，because Miss Jackson is retiring．公司已经计划举办一次聚会，以欢送杰克逊小姐退休。

A plan is on foot to invite the Minister of Health to visit our hospital．邀请卫生部长来我们医院访问的准备工作正在进行。

on good terms . on good terms with . enjoying friendly relations . enjoying friendly relations with （与…）和睦相处

The two neighbouring countries are on good terms．这两个邻国和睦相处。

The two brothers had not been on good terms since their father died，and there was a dispute over the will．兄弟俩自从父亲死后一直不睦，他们对遗嘱有争议。

We are not on very good terms with the people next door．我们和邻居关系不太好。

on guard . watchful警惕；警戒

The police warned people to be on guard for pickpockets during the Christmas rush．警察警告人们在圣诞购物高潮时谨防小偷。

Be always on guard against complacency．要时时警惕自满情绪。

 on hand . nearby；within reach附近；在手头

Do you happen to have any aspirin on hand? I seem to be getting a headache．你身边有阿斯匹林吗? 头痛。

Always have your dictionary on hand when you study．学习时要随时将词典放在手边。

 on hand . present出席；在场

You'd better wait here so you'll be on hand when you're needed．你最好在这儿等着，以便需要你的时候你在场。

Mr．Baker's secretary is always on hand when he appears in public．贝克先生出现在公众面前时，他的秘书总是在场。

 on hand . in stock；available现有（存货）

We have some new woollen goods on hand．我们现有一些新羊毛织品。

The department store has a large stock of goods on hand．这家百货商店现有大量存货。

on ice . sure to be won有获胜（成功）的把握

With their lead they had the game on ice．由于他们得分领先，他们有了赢得这场比赛的把握。

on ice . away for safekeeping or later use留待后用；搁置

The plan for the new book is on ice at the moment． I've been busy with too many other things．写新书的计划暂停。我一直在忙于做太多其它的事。

He will have to put his vacation plans on ice until his debts are paid．在还清债务之前，他只好搁置度假计划。

on leave . absent with permission请假；休假

The soldier is absent from his regiment on leave．这位士兵休假，不在队上。

on my honor . upon my word发誓；一定

I promise on my honor not to betray the secret．我发誓不泄露机密。

on no account . definitely not决不

On no account should we go out in this big storm．我们决不能在这场大暴风雨中外出。

Don't on any account leave your baby alone in the house．切不可将婴儿独自留在家里。

 on occasion . occasionally； now and then偶然地；有时

I went swimming on occasion in summer．夏天我有时去游泳。

I meet him on occasion at the club or in the theatre．我在俱乐部或戏院里有时能遇到他。

On occasion we feel like celebrating and have a party．我们有时喜欢来个聚会庆贺一番。

 on one's best behavior .  on one's good behavior . behaving right行为规矩

While his father was around，the boy was on his good behavior， but when the father left， the boy soon got into mischief．父亲在场时，这孩子规规矩矩，但父亲一走，他马上就调皮起来。

The naughty boy is on his best behavior today．今天这个调皮鬼表现很好。

on one's feet . standing or walking站立或步行

Before the teacher finished asking the question， George was on his feet，ready to answer it ．老师的问题还没问完，乔治就已经站起来准备回答。

How do you keep on your feet so long? 你怎么坚持站了这么长时间?

on one's feet . recovering恢复（身体）

Jack is back on his feet after a long illness．杰克病了好长时间，现在恢复健康了。