在这里，我们将只回答一个问题。这个问题有关定语从句，是一位读者提出来的。他说有这样一句话：
(1)Something unexpected has happened which prevents me from keeping my promise.
他问到这里的 which 从句是否是非限制性定语从句，如果是，为什么其前没有逗号？如果是限制性定语从句，是否可移到主语的后面？
这里的 which 从句不是非限制性定语从句，而是一限制性定语从句。限制性定语从句一般皆紧置于其所修饰的名（代）词之后，但有时，一般由于其本身太长而不得不与其所修饰的名（代）词分开，这种定语从句语法上唤作隔离定语从句，它一般不可直接放在其所修饰的名（代）词之后。就以上述句（1）为例，如将 which 从句移至其所修饰的代词 something 之后，全句显然就会头重脚轻，失去了平衡。隔离定语从句常置于谓语之后，如句（1）中的 which 从句即被置于谓语 has happened 之后，再如：
(2)Why, I don't suppose anything happens that our Toff doesn't foresee . （that 从句置于 happens 之后，与其所修饰的代词 anything 分开）
(3)A new master will come tomorrow who will teach you German .（who 从句置于 will come tomorrow 之后，与其所修饰的名词 master 分开）
(4)In general those parents have the most reverence who deserve it . （who从句置于 have the most reverence 之后，与其所修饰的名词 parents 分开）
隔离定语从句也常可置于介词短语之后，如：
(5)They had done all for him they were going to do .
（从句 that they were going to do 置于 for him 之后，与其所修饰的代词 all 分开）
(6)Seven bodies have been found from a 4,000-ton ship with a crew of 30 that is missing after encountering a cyclone in Bohai Bay early on October 31 .（that 从句置于 with a crew of 30 之后，与其所修饰的名词 ship 分开）
(7)He brought something into her life that had never been there before and which she longed for now .（that 和 which 引导的两个隔离定语从句置于 into her life 之后，与其所修饰的代词 something 分开）
隔离定语从句有时亦可置于后置定语之后，上述句（1）中的 which 从句即亦置于后置定语 unexpected 之后，再如：
(8)There was an old man there who was smoking a long pipe . （who 从句置于后置定语 there 之后，与其所修饰的名词 man 分开）
(9)I have clients working who aren't half as pretty as you . （who 从句置于后置定语 working 之后与其所修饰的名词clients 分开）
隔离定语从句有时亦可置于状语从句之后如：
(10)You can leave a message if you like that can be given her when she gets done her work .（that 从句置于状语从句 if you like 之后，与其所修饰的名词 message 分开）
注意下面一句中的隔离定语从句则置于“介词短语+状语从句”之后：
(11)There was a deference about his manner when he addressed her that was new . （that 从句置于 about his manner when he addressed her 之后，与其所修饰的名词 deference 分开。这里 that 从句置于句末有被强调的含意）
关于隔离定语从句，就谈这么多吧。
