英语四级作文写作思路及范文：说明文

说明文的说明方法

1. 定义法(definition)

定义法是用下定义的方式去揭示事物本质特征或概念内涵。它能使读者迅速抓住本质属性和基本特点。此法的句型：

① is a/the of which/that ② relate to/involve/refer to

【例】

(1)Language is a system of arbitrary vocal symbols which is used for human communication. 语言是人类用来交际的任意性的语音符号体系。

(2)Intermediate goals relate to outcomes during the next few years.

(3)Short-term goals involve outcomes expected during the next 12 months.

2. 举例法(illustration)

举例法就是举出实际事例来说明事物的方法，是最常见，往往也是最有效的阐释模式。

专家提醒

举例时应挑选具体、典型且有能力表达清楚的例子，并注意按照一定的顺序编排。

请看上述范文第二段：For instance引出lifetime goals的实例，如，赢得研究奖金、出版有影响书或文章、获得大学的系主任职位、获得国家自然科学基金及大公司稳定的顾问职位。

3. 分类法(classification)

分类法就是把说明的对象，按一定的标准划分成不同类别分别加以说明的方法。如：上述范文介绍人生的三种目标，并按照时间的长短对终生目标、长期目标和短期目标做了分类说明。

4. 比较法(comparison)

比较法是用一个事物和与其有联系的其他事物加以对比的说明方法。目的是为了帮助读者准确地区分事物，通过对比达到对该事物的深刻认识。

如：上述范文对三种人生目标在时间上和实际操作上进行了比较，并阐明了彼此的联系。

(1)Lifetime goals should be written out.

(2)Like lifetime goals, these are measurable and clearly stated.

(3)These goals are more performance oriented, and they help with achievement of intermediate goals.

5. 数字法(statistics)

数字法是运用数据来表明事物的本质和特点，准确合理的数据使文章精确可信。

【例】

(1)Nearly half of all Americans over age 20 wear a bridge or denture，and more than 20 percent have complete upper and lower denture. By age 50, one out of every two persons has gum disease.

(2)And it seems sensible to wait. One quarter of all marriages between people under twenty-one end in divorce. In Britain in 1972, there were 124,248 divorces.

范文参考

（1）Goals

Everyone has goals. Many people do not reach their goals for lack of planning. These three sets of goals should be developed: lifetime, intermediate and short term.

Lifetime goals should be written out. These goals should be clear and reasonable. For instance, the goal to win a research prize is clear and measurable. Other lifetime goals might include publishing a certain number of influential books or articles, earning a departmental chairmanship at a major university, successfully competing for a grant from the National Science Foundation or securing a consultantship with a big corporation.

Intermediate goals relate to outcomes during the next few years. For the beginning doctoral student, intermediate goals may include completion of course work and preparation of a doctoral research proposal. Like lifetime goals, these are measurable and clearly stated.

Short-term goals involve outcomes expected during the next 12 months. These goals are more performance oriented, and they help with achievement of intermediate goals. Examples of short-term goals are earning an A in a course, learning how to program a computer or performing an experiment.

（2）A Famous Clock

When you visit London, one of the first things you will see is Big Ben, the famous clock which can be heard all over the world on the B.B.C. If the Houses of Parliament had not been burned down in 1834, the great clock would never have been erected. Big Ben takes its name from Sir Benjamin Hall who was responsible for the making of the clock when the new Houses of Parliament were being built. It is not only of immense size, but is extremely accurate as well. Officials from Greenwich Observatory have the clock checked twice a day. On the B.B.C. you can hear the clock when it is actually striking because microphones are connected to the clock tower. Big Ben has rarely gone wrong. Once, however, it failed to give the correct time. A painter who had been working on the tower hung a pot of paint on one of the hands and slowed it down!