(一)说明文的说明对象
说明文的说明对象可以是具体的客观事件、人物、自然环境，也可以是某些抽象的东西，比如原理、概念、定律、思想等。
(二)说明文的应用范围
说明文可以是报告、文献、教材、历史资料、广告、说明书、宣传等。
(三)说明文常用的写作方法
常用的说明文写作方法有：1定义法。2举例法。3.分类法。 4.比较对比法。5.比喻、比拟法。6.时间顺序法。7.空间顺序法。8.图表说明法。9.数字说明法。
10.描述说明法。
(四)说明文的写作要求
说明文要求重点说明一个问题或事物或事物的一个方面，要求观点明确、举例充分、详略得当、条理清楚、层次分明。
(五)实例分析
【例1】Title：How to Build up Your Vocabulary
Directions：1The easiest way to increase the vocabulary.
2The way of saving time.
3.The use of vocabulary.
How to Build up Your Vocabulary
A vocabulary of a new language is acquired in several ways：by guessing from the context，by use of the dictionary in connection with our reading，and by special vocabulary drill apart from reading.Shall we build up our vocabulary slowly and laboriously so that years later we can read fluently;or shall we learn our vocabulary at the same time that we are reading? Perhaps the easiest and most interesting way to increase the vocabulary is to get a story written in an easy style(the teacher or librarian can recommend one)and read it as a story.To read a selection as a story means to read whole sentences and paragraphs rather than to translate word for word.Even though we lose the meaning here and there，we finally grow familiar with certain words without looking them up at allOf course，this is just what we do in reading stories in our own language.Such reading gives us a better feeling for idiomatic usage and for syntax than would be gained from wordforword translation.(该段主要介绍了几种扩大词汇量的方法，但着重介绍了其中的一种，即“阅读简易小说”。这种说明方法称为“比较法”。)
This“feeling”for vocabulary and usage must，of course，be verified and strengthened by definite study of rules and idioms.Rules of grammar are timesavers.A rule is a statement of the way things are ，or the way things act.(定义法)We might learn all the ways of the words in a given language by reading many books that have been written in it，and noticing the usual way of behavior of words.But we do not need to do this because it is what has been done by the men who tell us what the rules are.By using their work，we can save time and energy and make more rapid progress.(该段主要给我们讲述了在单词记忆过程中如何节约时间的问题，并且向我们推荐了一种比较好的节省时间的方法。说明方法有“对比法”和“下定义法”。)
Idiomatic expressions of whatever length should be learned as a whole，as though each expression were a word in a vocabulary.They should be learned by use both in reading and in conversation，and by drill.(该段主要介绍如何才能加深对词汇的记忆，并指出了几种记忆词汇的方法。)(324 words)
分析：该篇短文运用“比较法”、“对比法”以及“下定义法”向我们介绍了记忆词汇和巩固记忆的诸多方法。条理分明，语言浅显易懂，逻辑顺序合理。
