为了简洁起见，有的状语从句(如时间状语从句、条件状语从句等)有时可省略从句的主语和部分谓语(尤其是当从句主语与主句主语一致，且从句谓语包括有动词be时)：
She fell asleep while (she was) doing her homework. 她在做作业时睡着了。
He kept silent when (he was) asked why he was late. 问他为什么迟到，他一言不发。
Although (it was) built 100 years ago, the bridge is very strong. 虽然建于100年前，但这桥还是很牢固。
有些由if构成的省略结构，已属固定短语，如if any, if necessary, if possible, if not, if so等：
There are few, if any, mistakes in that book. 那本书就是有错误也不多。
If necessary, ring me at home. 如果必要，可以打电话到我家找我。
If possible, I wish to go there next summer. 如果可能，我希望明年夏天去。
He may be busy. If so, Ill call later. If not, can I see him now? 他可能很忙，要是这样，我以后再来拜访。要是不忙，我现在可以见他吗?
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Work your socks off 拼命干活
A sense of belonging 归属感
Practical and pragmatic “实用的”两个词的区别
Objective and purpose 目标和目的
At each other’s throats 唇枪舌战地争吵
Pay through the nose for something 出高价，花大价钱
Is breast cancer linked to night shifts? 乳腺癌与上夜班有关系吗？
Europa moon 'spewing water jets' 木卫二表面“喷射出水汽”
Been to vs gone to 语法辨析
To be on the same wavelength 意气相投
Strapped for cash 手头紧
Dressed to the nines 衣冠楚楚
Have egg on your face 狼狈不堪
Parcel, sack, box 包裹类词语
Football and soccer 两个词的区别
To have deep pockets 资金雄厚
Butterfly numbers drop a mystery, say experts 英国蝴蝶数量下降现象令专家费解
Have your feet on the ground 脚踏实地
To pop the question 求婚
Talk nineteen to the dozen 说话很快，喋喋不休
Under someone's thumb 受人控制
Passion and enthusiasm 两个词的区别
Almost, nearly, more or less “差不多”的三个近义词
To wind someone up 捉弄、惹恼某人
To have a crush on someone 迷恋某人
Armed to the teeth 全副武装
To hit it off (with someone) 一见如故
To harp on about something 喋喋不休
A nest egg 储备金
Labour, labourer, workforce, worker 与“工作”相关的四个单词