根据不同的写作目的，篇章写作一般分为四种主要类型：
1）Narration（叙述文）
2）Description（描写文）
3）Exposition（说明文）
4）Persuasion and argumentation（议论文）
从本单元起，我们将着重介绍在大学英语四级统考中应用得最为广泛的说明文。说明文常用于阐述事物的特征、本质、性能、结构、用途等。抽象的说明是很难让人理解和接受的，所以在进行说明时我们常用举例法、比较与对照法、定义与分类法、过程分析法和因果法等写作方法推展段落和篇章。这些方法均已在段落推展法之四、五、六、七、八、九中一一做了介绍。以下我们将在第二十三、二十四、二十五、二十六及二十七单元中分别用这些方法对篇章的推展作进一步的讨论。
另外，在今后的各单元中，我们将尽量少用汉语，以便使大家养成用英语思维的良好习惯。
23．1 举例法Examples
在篇章写作中，我们常用实例来对自己的观点或文章的主题思想进行说明、解释，使抽象、难解的事物具体化。这不仅有助于读者感受到我们的观点，而且可使文章读起来生动、有趣。切记：举例时一定要典型，能为文章的主题思想服务；而且还要生动、有趣，给人以深刻印象。
23．2 Comparison of Two Model Essays（两例范文的比较）
1）My Bad-Tempered Father My father is easily angered by normal，everyday mistake．One day my father told me to wash the car and cut the grass．I did not hear exactly what he said，and so I asked him to repeat it．Then he went into a hysterical mood and shouted，"Can't you hear？"
Another time he asked my mother to go to the store and buy groceries with a fifty-dollar bill，and told her to spend no more than twenty dollars．She spent twenty-two dollars．As soon as he found out，he immediately grabbed the change from her and shouted that she was never to do any errands for him again．He did not speak to her for the rest of the day．
My father also gives my older brothers a hard time with his irritable moods．One day，he told them to be home from their dates by midnight；they came home at 12∶15．He informed them that they were grounded for three weeks．
To my father，making a simple mistake is like commiting a severe crime．
2）My Generous Grandfather My grandfather is the most generous person I know．He has given up a life of his own in order to give his grandchildren everything they want．Not only has he given up many years of his life to raise his children properly，but he is now sacrificing many more years to his grandchildren．
His generosity is also evident in his relationship with his colleagues，neighbors and friends．He has been responsible for many good deeds and has always been there to help all the people around him in times of trouble．Everyone knows that he will gladly lend a helping hand．
He is so generous that you almost have to feel sorry for him．If one day he suddenly became selfish，it would be earthshaking．That's my grandfather．
23．3 Analysis of the Two Model Essays（两例范文的分析）
The first passage is more effective，for it offers specific examples that show us the father in action．We see for ourselves why the writer describes the father as bad-tempered．It also uses transitional phrases or sentence to organize the passange more clearly and logically．Using"one day"，the writer introduces us the first example of his father's hot temper；"Another time"indicates the second example and the transitional sentence"My father also gives my older brothers a hard time with his irritable moods"indicates another example will follow．It is the supporting examples and the transitional devices that make the passage more effective and coherent．
The second writer，on the other hand，gives us no specific evidence．The writer tells us repeatedly that the grandfather is generous but never shows us examples of that generosity．Just how，for instance，did the grandfather sacrifice his life for his children and grandchildren？Did the grandfather hold two jobs so that his soncould go to college，or so that his daughter could finish her education？Does he give up time with his wife and friends to travel every day to his daughter's house to baby sit，go to the store，and help with the dishes？We need to judge for ourselves whether the writer is making a valid point about the grandfather，but with out specific details we cannot do so．In fact，we have almost no picture of the grandfather at all．
Writing Assignment for Unit 23
Directions：Write a short passage of the title"My Sweet-Tempered Mother according to the given topic sentence．
Remember to provide specific details to illustrate your point and use transitional words or phrases to make your writing more clearly and coherently．You may write your passage on the good qualities of a person by using some of the descriptive words listed below．They are only suggestions，you can write about other qualities as well．
honest hardworking supportive modest
open-minded considerate independent good-humoured
cooperative energetic disciplined patient
generous trustworthy neat courageous
ambitious soft-hearted reliable unpretentious
My mother is the most sweet-tempered person I know．
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