說明文是以說明為主要表達方式用來說明事物，闡明事理的一種文體。它通過揭示概念來說明事物的特征、本質及其規律性，給人準確的科學知識或正確思想。一般可分為實體事物說明和抽象事物說明兩大類，詞典、教材、論文、實驗報告、產品說明書、廣告、解說詞及科學小品等都屬于說明文。

　　按寫作方法,英語說明文主要分為下面六種類型:

　　1.例證法

　　這是用具體例子來說明人或事物的特征、本質及其規律的方法,所用例子必須有代表性、典型性,能體現人或事物的本質特征。這是用特殊來說明一般的方法。通常在主題句后,用 For example 或 For instance 等短語引導出具體的例子。例如:

　　Our life today depends very much on energy. For example, machines have made our life easier than it used to be. The machines use energy, and energy is needed for heating, lighting, communications, carrying goods-everything. Factories use a great deal of energy to make the things that we use and buy and sell.

　　這段主要是講能源問題。第一句為主題句,概括地說出"我們目前的生活很大程度上依賴能源"。接著用舉例的方法從三方面說明能源的作用。

　　2.定義法

　　下定義就是給說明對象一個明確概念。這是科學而嚴密的說明方法。它既能揭示事物的本質特征,勾勒其大概,描繪其輪廓,同時也能確定事物的范圍和界限。下定義是多方面的,可以給人、事物、思想等下定義。例如:

　　An ideal teacher must have the following characteristics. He should know his subject, but he can make mistakes if he is willing to learn. His personality is as important as his scholarship. An ideal teacher must be enthusiastic. He should be a bit of an actor and he shouldn't be afraid to show his feelings and express his likes and dislikes. An ideal teacher is one who grows, learns, and improves himself along with his students.

　　本段的展開是通過對"一個模范教師"下定義的方法,關鍵詞"ideal teacher"在文中多次重復,能加深讀者的印象。

　　3.分類法

　　分類法是對同屬不同類或同類而不同種的人或事物,根據不同性質進行分門別類地說明的方法。分類是人類認識客觀世界的重要手段之一。分類必須遵守分類規則,使分類對象具有統一屬性,依據同一分類標準,并使分類的子項相互排斥,不互相包蘊。例如:

　　As far as political views are concerned, people fall into three categories. First are the conservative people. Conservatives are opposed to sudden or great changes. Second are the liberal people. These people are in favor of progress and reform. But their opinions often seem too idealistic. Third are the moderate people. The moderates keep everything within reasonable limits. They are more practical in this hard world. In my opinion, most people seem to belong to this group.

　　本段把人按政治觀點分為三類:保守派(conservative people)、自由派(liberal people)和溫和派(moderate people),并對他們各自的特征進行了簡要的分析。

　　4.因果關系法

　　事物變化的原因和結果是緊密相關的。如果某個現象的存在必然引起另一個現象的發生,那么,這兩個現象之間就具有因果關系。因果關系包括"由果推因"(由結果去推測原因)和"由因推果"(由原因去推測結果)兩種情況。因果關系符合人們的日常思維邏輯,因而在寫作中得到廣泛應用,常用 because, as, since, so, now that, if...then, the reason is that...等表示因果關系。例如:

　　Of the four seasons, I like spring best. I prefer spring because it is a season of much joy and gaiety. New life bursts out everywhere. Plants wear a green coagain and colorful flowers blossom in gardens and mountains. The old come outdoors for fresh air and the young plan for outdoor activities. Life becomes so energetic and happy.

　　第一句為本段主題句,末句是總結句。在主題句后, 作者用了四個句子闡述自己喜歡春天的理由。

　　5.比較對照法

　　有意識地把兩種相反、相對的事物或同一事物相反、相對的兩個方面放在一起,用比較的方法加以描述或說明,指出其相同點,這種寫法叫做"比較";指出其不同點,叫做"對照"。比較和對照各有不同的側重,但兩種方法經常結合使用。

　　進行比較對照通常有兩種方式。第一種方式采用"先A后B"的結構,即A1,A2,A3...; B1, B2, B3...。第二種方式采用"AB交錯"結構,即A1,B1;A2,B2;A3,B3...。第一種方式采用先A后B的結構實際上是把一個段落(或一篇文章)分割為兩部分,先全面講A,再全面講B,這樣做較難收到強烈的對比效果。多數人認為第二種方式比較好,因為把對比的雙方AB逐點交錯,可以避免行文的單調沉悶,對比的效果也會更鮮明突出。例如:

　　It is easy to be a winner. A winner can show his joy publicly. He can laugh and sing and dance and celebrate his victory. People love to be with winners. Winners are never lonely. Unlike winners, losers are the lonely ones of the world. It is difficult to face defeat with dignity. Losers can not show their disappointments publicly. They can not cry or grieve about their defeat. They may suffer privately, but they must be composed in public. They have nothing to celebrate and no one to share their sadness.

　　這段采用先A后B的對照方式,闡述勝利者和失敗者的不同特征。這種寫法較易操作,但行文往往比較平淡單調。再來看看AB交錯的比較方式:

　　I like having a twin sister. When she’s happy, I’m happy. When she feels unhappy, I feel the same. Often, I know what she’s going to say. Sometimes, I know what she’s thinking. I like what she likes. I hate what she hates. We like the same music, the same food and the same books.

　　這段采用AB交錯的比較方式,闡述孿生姐妹的相同特征。這種寫法較流暢自然,給讀者的印象也更鮮明突出。

　　編輯推薦：

　　2013 年6月大學英語四級(CET-4)高頻詞匯匯總

　　2013 年大學英語四級考試寫作輔導大全