6．　因果分析法(cause and effect)
        在阐述某一现象的段落中，常采用因果分析法。例如：
        　　
        The role of women in today's society is changing. One reason is that women have begun to assert themselves as independent people through the women's movement. Also, women are aware of the alternatives to staying at home. Another reason is that increasing numbers of women who enter new fields and interests serve as role models for other women. Moreover, men are becoming more conscious of the abilities of women and have begun to view their independence positively.
        　　
        本段中，主题句提出了一种社会现象，推展句则对产生这种现象的原因作出各种解释。 常用于因果分析法的连接词有：because, so, as a result等。
        
        7． 定义法(definition)
        　　
        在科普文章的写作中，定义法是必不可少的。通过下定义，可以使读者对该事物有一个更直接的认识。
        Automation refers to the introduction of electronic control and automation operation of productive machinery. It reduces the human factors, mental and physical, in production, and is designed to make possible the manufacture of more goods with fewer workers. The development of automation in American industry has been called the "Second Industrial Revolution".
        　　
        这一段文字使我们了解了 "automation" 和 "Second Industrial Revolution" 两个概念，分别由 "refers to" 和 "been called" 引出。
        常出现在定义法中的词语有：refer to, mean, call等。