不完整的句式没有独立的从句;而冗长的句式则有两个以上的从句，而这若干从句之间并没有恰当地衔接。这两种错误都是我们应该努力避免的，具体做法如下。
不完整的句式
正式写作中的每句话都必须有独立从句。所谓独立从句，就是包含主语、谓语，并且不以下述连词作为句子开头：
After if than whenever although in order that though where as provided that unless whether because since until while before so that
错误：Global warming. This is what the scientists and journalists are worried about.
正确：Global warming is the cause of concern for scientists and journalists.
注意，以并列连词——and、but、or、nor和for作为单句的开头，则是可以接受的。例如：
正确：Most people would agree that indigent patients should receive wonderful health care. But every treatment has its price.
冗长的句式
在时间紧张的情况下，不少学生写出来的句子没有标点连接，或者只有逗号。例如：
Current insurance practices are unfair they discriminate against the people who need insurance most.
我们有三种修改方法：
1)标注句号：Current insurance practices are unfair. They discriminate against the people who need insurance most.
这样，一个独立的句子就变成几个独立的从句。
2)标注分号：Current insurance practices are unfair; they discriminate against the people who need insurance most.利用分号把具有独立意义的句式分开，但同时向读者表明句子表示的含义之间存在一定联系。
3)利用连词：Current insurance practices are unfair in that they discriminate against the people who need insurance most.这也是最有效的修改方法，从句仍然是独立的，同时也表明了从句之间的联系。
出现冗长句式还有一个原因，就是误用however、nevertheless、furthermore、likewise、therefore等副词。例如：
错误：Current insurance practices are discriminatory, furthermore they make insurance too expensive for the poor.
正确：Current insurance practices are discriminatory. Furthermore, they make insurance too expensive for the poor.
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