where定语从句修饰抽象名词

连词+省略结构”的一种。这类结构归纳起来主要有以下几种类型：
一、连词+介词
While at college, Delia wrote a novel. 上大学时，迪莉娅写了一部小说。
Once in the examination hall, he forgot about all this. 他一进考场，这一切他都忘了。
While in London, he studied the English labour movement. 在伦敦时他研究了英国的工人运动。
二、连词+形容词
He acted as if certain of success. 他表现得对成功很有把握似的。
If possible, let me know beforehand. 如果可能，可在事前通知我。
Though exhausted, he stayed up late. 尽管疲惫不堪，他仍很晚才睡。
Whenever possible, the children play outside. 每当可能，孩子们总在外边玩耍。
Avoid structures of this kind wherever possible. 只要可能，都要避免这种结构。
Her daughters were of some help, however small. 她的女儿们总能帮些忙，不管多小的忙。
三、连词+现在分词
She tremble a little while doing so. 她这样做时稍稍颤抖了一下。
He tends to get carried away when watching wrestling on TV. 他一看电视中的摔跤就很兴奋。
They were surprised by her openness when talking about her private life. 她谈起私生活时非常坦率，大家都很吃惊。
注：以下两句中的before不是连词，而是介词，其的-ing动词为动名词，而非现在分词：
Before giving evidence the witness had to take an oath. 证人作证前要先宣誓。
It would be unwise to buy the house before having it appraised. 买房子不事先估价是不明智的。
四、连词+过去分词
He will come if asked. 他如被邀就会来。
When asked, she confirmed that she was going to retire. 有人问她时，她肯定了她将要退休。
While locked up in prison, she wrote her first novel. 她在狱中写出了第一部小说。
When taken according to the instructions, the drug has no side effects. 若按说明服用，本药无任何副作用。
五、连词+不定式
Success in business is simply a matter of knowing when to take a chance. 商业上的成功就在于把握时机。
Smiling pleasantly, the stranger turned as if to speak to me. 那个陌生人面带愉悦的笑容，转身向我，似乎想对我说话。
【温馨提示】
1. “连词+省略结构”通常可视为一种紧缩的状语从句，即认为是省略了从句的主语（与主句主语一致）和主语后的动词be。如：
Look out for car’s when (your are) crossing the street. 过街时注意车辆。
He acted as if (he was) certain of success. 他的举止就像一定会成功一样。
有时可视为省略了it is（其中的it并非主句主句）。如：
lf (it is) possible, please let me know by this evening. 如果可能的话，请在今晚以前告诉我。
Where (it is) necessary, improvements will be made. 哪儿需要，就在哪儿改进。
2. 并不是所有的状语从句都可以用以上办法来紧缩的，如原因从句就不能用这种办法来处理