一、主要子句和从属子句之别
✏️ 范例1：
Henry and Peter met on August 10, 2005. The place where they met was a diner in downtown Manhattan. They wanted to discuss the terms of a business proposal. They had little idea that they would one day become billionaires.
这个段落的三个句子都以主词开头，接着是动词，可是三个句子之间的关系却不太清楚，从句子的安排上看不出来主从的关系。如果我们将背景资讯放在从属子句，要强调的部分就可以凸显出来了：
✏️ 范例2：
When Henry and Peter met at a diner in downtown Manhattan on August 10, 2005, to discuss the terms of a business proposal, they had little idea that they would one day become billionaires.
这里的从属子句交代了亨利和彼得会面的背景资讯，包括了地点（在曼哈顿的市中心）、时间（2005年八月十日）和目的（讨论一项商业提案的内容），而主要子句在后面，凸显了会面在日后带来的结果（成为亿万富翁）。如果我们写作时可以善用从属子句和主要子句的区别，句子会显得更有条理。
二、片语和子句之别
另外，改写前的例子将背景资讯用独立的句子表达，读者不容易判断这些资讯是否比主要的内容（他们不知道自己将成为亿万富翁）重要。改写过的例子则将各项背景资讯用片语（at a diner in downtown Manhattan、on August 10, 2005 及 to discuss the terms of a business proposal）表达，而主要的内容用独立子句（they had little idea that they would one day become billionaires.）显示其重要性。
除了背景资讯，表达因果关系的句子也可用从属结构表达，试比较以下两句：
✏️ 范例1：John was tired and sleepy, and he went to bed early.
✏️ 范例2：Tired and sleepy, John went to bed early.
第一个例子有两个对等子句，前者（John was tired and sleepy）是因，后者（he went to bed early.）是果。我们可以将原因用从属结构表达，如同第二句的片语 tired and sleepy。
