英语说明文的写作方法（二）
4.定义法（definition）
定义法也是英语说明文中常用的写作手法，特别是在对具体事物概念进行说明时经常使用。定义法的基本要素是定义句。英语中常见定义句的模式是：
被定义对象is所属类别+限制性定语
可以看出，定义句中限制性定语越详细，定义就越精确，比如：
A bat is a small mouse-like animal that flies at night and feeds on（以……为食品）fruit and insects but is not a bird.
其实，在英—英词典中，对英语单词的英文解释就是定义法的典型例子。比如，看看Longman词典对student和teacher的定义是很有意思的：A student is a person who is studying at a place of education or training. A teacher is a person who gives knowledge or skill to sb. as a profession（专业）。
5.顺序法（sequence of time，space and process）
顺序法是指按时间、空间或过程的顺序进行说明的一种写作手法。比如按照时间顺序介绍一个科学家的生平，用空间顺序阐述逐渐开发西部的重要意义，用过程顺序法解释葡萄酒的生产过程等等。
下面这篇学生作文就是用顺序法写成的：
Coal
Coal underwent（经受）many changes before it became the bright，brittle（脆的），black substance which we now use. During ancient times（在上古时代），when the earth enjoyed a very warm and wet climate，the land was covered with large forests and big plants. As time went on，the ground changed and began to sink（下沉）a little. These very large numbers of trees and vegetables received a deposit（沉淀）of sand and clay. This layer of sand and clay pressed upon the layer beneath and prevented it from contact with air. These trees and plants received the pres sure and changed its appearance.
Generations after generations（几世纪后），as the ground kept gradually sinking，another layer of sand and clay was again deposited（积聚）above the layers already formed. A great pressure was thus exerted（作用）and the peat（泥煤）was changed into the black and brittle substance which is known as coal.
Coal is a kind of mineral which is formed by nature as above stated. It is an important industrial material and is chiefly used as fuel. It is very valuable in the industrial world. The place where coal deposit is called a coal mine（煤矿）。 In China，coal mines are largely found in the north-west part of the country. Shanxi is a famous province for producing coal. It has the most coal of China.
6.分类法（classification）
分类法是将写作对象进行分类说明的一种写作手法。比如：著名的英国哲学家弗朗西斯·培根（Francis Bacon）在其脍炙人口的《谈读书》（Of Studies）一文中就用到了分类法：
Some books are to be tasted，others to be swallowed，and some few to be chewed and digested，that is，some books are to be read only in parts，others to be read，but not curiously，and some few to be read wholly，and with diligence and attention. Some books also may be read by deputy，and extracts made of them by others； but that would be only in the less important arguments，and the meaner sort of books…
参考译文：书有可浅尝者，有可吞食者，少数则须咀嚼消化。换言之，有只须读其部分者，有只须大体涉猎者，少数则须全读，读时须全神贯注，孜孜不倦。书亦可请人代读，取其所需摘要，但只限题材较次或价值不高者……
——转摘自《英汉翻译教程》（张培基等）
可见，如果能够根据具体情况，选用合适的写作手法，就可为文章增添无穷的魅力。
除了上述提到的6种展开英语说明文主题的写作方法之外，还有因果法、归纳法等其他方法。但相比之下，对于中学生来说，上述6种方法是首先值得掌握的。另外必须指出的是：在一篇文章中往往是以一种写作手法为主，同时辅以其他写作手法。有时，甚至会几种写作手法混用而不分主次。因此，必须根据具体情况，选用合适的展开主题的写作手法，才能写出优秀的英语说明文。
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《高中英语语法-英语说明文的写作方法（二）》由留学英语组编辑整理(m.liuxue86.com)