从结构分，英语句子可总体分为三大类，即简单句、并列句和复合句，而复合句又包含复杂句和复杂复合句两种，其分法，各家自有道理，在此，我们以三分法来介绍句子的分类：
1.简单句
简单句只含有一个主谓结构，句子的各个成分都不是句子，即单词或短语构成的句子。
e.g. (1) They enrich our cultural life.
(2) It brings us a lot of pleasure and amusement.
(3) Meanwhile milk had been accepted by the masses， because of its abundant nutrition.
(4) More importantly， relatives， neighbors and his teachers should give the very kid much love as possible to make him feel least abandoned.
以上四句，虽然长短相距很大，但每句只有一组主谓结构，故均为简单句。
2.并列句
句中含有一个以上互不依从的主谓结构，各主谓结构构成的分句通常由并列连词（and，but，while，or 等）连接，这类句子就称为并列句。
e.g. (1) Solving the problem of traffic jam is not an easy job and I don"t think any individual or organization can easily handle it.
(2) Some professors prefer to control discussion， while others prefer to guide the class without dominating it.
(3) I used to meet several vegetations but I have never heard of a nation that advocates vegetation diet.
3.复合句
句中含有一个以上的主谓结构，其中一主谓结构充当另一主谓结构的某个成分，如主语、宾语、定语、状语、补语或同位语。充当成分的结构就称为相应成分的从句，而整个句子就称为复合句。
e.g. (1) At that moment only a language that can be accepted and understood by most of the people such as English， French， Arabian and so on will function.
(2) But the problem is that the cost for telephone calls is so high that many can not afford it.
按结构把句子分成简单句、并列句和复合句，其划分的范畴是在一个完整句（句号、问号或感叹号等划定）范围内来分析，因此在写作中我们要尽可能养成正确标点的习惯，以提高写作的语感。
（第三节）句子使用目的分类
英语句子按其使用目的分为四类： 陈述句、疑问句、祈使句和感叹句，写作中，陈述句使用最频繁，其他用得相对少些。
一、陈述句
陈述句用来说明一个事实或一种看法，通常以句号结尾。
e.g. (1) It calls for the joint efforts of the government， the young and the old people themselves.
(2) It prevents children from being polluted by some negative influence.
二、疑问句
疑问句分为一般疑问句、特殊疑问句、选择疑问句和反意疑问句四类。
1.一般疑问句以助动词、情态动词、be动词或have开始，要求以yes或no回答，有时certainly， perhaps， not at all等也可回答此类文句。
e.g. (1) Will their expectation come true？
(2) Can further scientific advance help the world solve the problem of future food supplies？
(3) Then couldn"t we live in the fresh air while enjoying the mobility of cars？
2.特殊疑问句以一个疑问代词或疑问副词开头，后面跟一个一般疑问句。
e.g. (1) If the students are forced to wear uniforms everyday， how can they develop their individuality and creativity？
(2) Since both film and TV have respective advantages， why not make most of these two types of entertainment.
(3) In what kind of work situations do they perform well？
(4) What did we use to do before there was no television？
3.选择疑问句提供两个由or 连接的供选择答案，句子结构和一般疑问句差不多。
e.g. Today when the global economy is in depression， how will you make the choice to domesticate animals with an empty stomach or to solve the living problem with the animals as the source of food and clothing？
4.反意疑问句起反问读者或通过反问语气肯定某种事实。
e.g. (1) He has done the job very well， hasn"t him？
(2) She is the tallest girl in her class， isn"t her？
三、祈使句
表示请求、命令、叮嘱、邀请或规劝等，谓语动词用原形这种句子的否定以do not或never 引导，其主语通常不出现。
e.g. (1) Let good advertisements facilitate communication between business people and the public， and help keep the business world moving.
(2) Never bring your work home. Leave it in your office.
四、感叹句
表示说话者的惊异、高兴或气愤情绪，常用what 和how 来引导，what用来修饰名词，how 用来修饰形容词、副词和动词。
e.g. (1) What a pleasure it is to have a friend with the same taste！
(2) How beautiful the landscape is！
以上各节，主要分析句子自身的构成成分、结构类和作用。这些知识是学习者应该了解和掌握的。
（第四节）有效句子的基本特征及常见错误分析
一、句子基本特征
一句好的英语句子，除语法要正确，还应该意境优美，表意清晰，具有可读性和欣赏性，具体包含下列特征：
1.完整性（unity）
即只包含一个并且完整的意义，句子的各个部分都应围绕句子中心展开。
e.g. (1) Born in a small town in South China in the early 50s， he grew up to be a famous musician. 该句子之所以是病句，它含有两个意义，Born in a small town 和grew up to be a famous musician 之间缺少内在的因果联系，应该写成两句，并加入一些信息把两句连起来。
改写为：He was born in a small town in South China in the early 50s. In his childhood he liked to sing. Later he entered a music conservatory. In the 70s， he became an accomplished musician.
再分析下句：(2) Michael Jordan is one of the greatest basketball players. 此句错在意义表达不完整，句中的最高级，没有比较对象或比较范围。
改写为：Michael Jordan is one of the greatest basketball players in the world.
2.连贯性（coherence）
即句中各部分过度顺畅、排列正确、指代明确、逻辑关系清晰。
e.g. Upon entering the classroom， the students stood up and said， “Good morning！”
该句看似没问题，细细阅读，发现句中逻辑关系不明，upon entering the classroom 究竟是指谁，处理的办法有两种，一是保留第一部分，entering的逻辑主语为老师，可改写为：Upon entering the classroom， the teacher was greeted by the students with “Good morning！”；二是保留第二部分，句子的第一部分应该成从句形式：改写为：When the teacher entered the classroom， the students stood up and said，“Good morning！”好些。
3.简练性（conciseness）
即句子不含多余的词。
e.g. She returned in the early part of the month of August.
改写为： She returned in August. 即可完全表达清楚。其余的均为多余。
4.强调性（emphasis）
句子强调方式主要有：用词、重复、标点、符号、句子的结构顺序等。不论何种方式目的就是突出重要内容。
(1) 通过从句来强调。
e.g. Every Spring Festival we all go to my grandfather"s house. It is near Suzhou. Suzhou is an attractive city. Now my parents live there.
改写为：Every Spring Festival we all go to my grandfather"s house. It is near Suzhou， an attractive city where my parents now live. (stressed) 原句本意想突出的内容是Suzhou，由于第2、3句和第4句三句都是结构相同的并列分句，结果未达强调的目的。修改后3个句子合成一个由主句带一个定语从句的复合句，效果就明显多了。
(2) 通过平行结构：重要性升序排列（即从不重要到最重要顺序排列），对仗结构。
e.g. ① With this faith we will be able to work together， to pray together， to struggle together， to go to jail together， to stand up for freedom together， knowing that we will be free one day. 本句采用重要性升序结构来陈述6个不定式，为强调be free one day为最高奋斗目标做铺垫。
② In prosperity， our friends know us； in adversity， we know our friends. ( 采用对比结构：stressed。)
③ An optimist sees the rose； a pessimist sees the thorn. （采用对照的方式，比照双方用分号隔开，其结构为并列式，其内涵为反向或矛盾关系，形成鲜明的对比，从而产生综合的强调效果：stressed。）
(3) 通过句首位或者句末位，即用：（Periodic Sentences or Loose Sentences）
e.g.Because its winds sometimes go over 500 miles per hour and it has more energy than an atomic bomb， the tornado is one of the most destructive forces on earth， and it can strike without warning. (unstressed)
可改为：The tornado is one of the most destructive forces on earth because its winds sometimes go over 500 miles per hour， and it can strike without warning. ( stressed )或Because its winds sometimes go over 500 miles per hour and it has more energy than an atomic bomb， and because it can strike without warning， the tornado is one of the most destructive forces on earth. ( stressed ) 把the tornado is one of the most destructive forces on earth放置到句子开头或末尾就起到了强调tornado的破坏性之大--世界之最。
(4) 采用主动语态，相比而言，主动语态比被动语态表述更清晰、更直接、更生动形象，因此能起到强调的效果。
