句子成分的划分句子成分的划分主干：主，谓，宾分枝：定状补，表语，同位语，独立成分1．主语：是句子要说明的人或事物，是句子的主体，一般由名词、代词、数词、不定式或动名词等充当。
如：The car is running fast．（名词）We are students．（代词）One of my classmates is from Shanghai．（数词）Eating too much is bad for your health．（动名词）【注意】若不定式短语作主语常用it作形式主语，而把真正的主语（不定式短语）放在句后。
It's bad manners to spit in public places．（不定式）2．谓语：说明主语的动作或状态，也是句子的主体部分，一般由动词充当。
动词分为实义动词、连系动词、情态动词和助动词。
实义动词单独作谓语，连系动词与表语一起构成谓语，情态动词与省略to的不定式构成合成谓语，助动词与动词原形共同构成谓语部分。
如：【注意】谓语与主语在人称与数方面要相互照应。
He works in a factory．（实义动词）I felt cold．（系动词＋表语）How can I get to the station？（情态动词＋实义动词）They are working in a field．（助动词＋实义动词）3．宾语：是及物动词所涉及的对象，一般由名词、代词、不定式及动名词等充当。
如：He is doing his homework．（名词）They did nothing this morning．（代词）She wants to go home．（不定式）We enjoy playing football．（动名词）①有的动词可接双宾语，间接宾语指人，直接宾语指物。
这类动词常见的有：give，buy，lend，pass，tell，leave等。
如：He bought me a book．Pass me the ball，will you？（间宾＋直宾）直接宾语一般放在间接宾语之后，但若把直接宾语放在前面，则要在间接宾语前加适当的介词如to或for(make, do, buy)等。
如：He lent some money to John．Mr. Liu bought a dictionary for Tom．②有的动词常用不定式作宾语，而不能用动名词。
这类动词有：want，wish，hope，promise，decide，agree，choose，care等。
如：I hope to see you again．He promised to repair the radio as soon as possible.③有的动词一般只用动名词作宾语，而不用不定式。
这类动词有：enjoy，finish，mind，practise，miss，suggest，keep（on）等。
如：Do you mind my opening the window？I enjoy reading in the quiet garden on Sundays.④有的动词后接不定式与动名词含义不同。
a）forget to do表示“未发生的动作”，forget doing表示“已完成的动作”。
如：Don't forget to come here earlier tomorrow．（还没来）I forgot returning the book to him．（书已还给他了）b）stop to do（不定式为状语）表示“停下原来的事，去做另一件事”，stopdoing表示“停止做某事”。
如：I stopped to talk with him．（我停下来与他谈话。
）The students stopped talking when the teacher came in．（老师进来时学生们停止谈话。
）4．定语：用于修饰名词或代词，一般由形容词、名词、数词、不定式，分词短语等充当。
What a beautiful kite it is！（形容词）She is a chemistry teacher．He runs a clothes shop.（名词）There are two students in the classroom．（数词）We have something to do tomorrow．（不定式）The man in blue is my brother．（介词短语）分词（短语）作定语：The old man living next door is very kind to others.The pen made in the US is very expensive.There are five boys waiting over there.【注意】定语一般位于被修饰词前，但若修饰不定代词或不定式等短语作定语，则放在后面。
5．状语：用于修饰动词、形容词、副词或全句，一般由副词、介词短语、不定式短语或从句充当。
单个副词作状语一般放在被修饰词之前，短语或从句放在句首或句末。
A．副词（短语）作状语：The boy needs a pen very much.男孩非常需要一支钢笔。
（程度状语）The boy needs very much the pen bought by his mother.（宾语较长则状语前置）The boy needs a pen now.（时间状语）B. 介词短语作状语：In the classroom, he boy needs a pen. 在教室里，男孩需要一支钢笔。
（地点状语）Before his mother, Tom is always a boy. 在母亲面前,汤姆总是一个男孩子.(条件状语)On Sundays, there is no student in the classroom. 星期天,教室里没有学生.(时间状语)C. 分词（短语）作状语：He sits there, asking for a pen. 他坐在那儿要一支笔。
（表示伴随状态）Having to finish his homework, the boy needs a pen. 因为不得不完成作业，男孩需要一支笔。
（原因状语）Frightened, he sits there soundlessly. （因为）受了惊吓，他无声地坐在那儿。
（原因状语）D. 不定式作状语：The boy needs a pen to do his homework. 男孩需要一支笔写家庭作业。
（目的状语）To make his dream come true, Tom becomes very interested in business.E. 名词作状语：Come this way! 走这条路！（方向状语）【注意】enough作状语只能放在被修饰词之后。
如：He is old enough to go to school．6．补语A. 主语补足语，通常位于主语之前或谓语动词之后，当然放在谓语动词被动语态的过去分词之后，①主语补语位于主语之前，后有逗号例：Tired and sleepy, I went to bed②有时位于主语之后，前后皆有逗号例：Chen, only 1.30 meters tall, won the first prize.③位于谓语动词之后例：He died young.He was found died.④除形容词外，名词、数词、不定式，分词，介词短语，从句也可作主语补足语。
例：He came home quite changed，过去分词短语作主语补足语。
含不定式、现在分词、过去分词作宾补的句子转换成被动语态后，原来的宾补即为主补。
例如：His father made him do a lot of housework after school.= He was made to do a lot of housework after school by his father.I heard him singing an English song in the classroom.= He was heard singing an English song in the classroom.The boy saw the dog tied to the tree.= The dog was seen tied to the tree by the boy.B.宾语补足语（1）英语中有些及物动词，除有宾语外，还要有一个宾语补足语才能使句子的意思完整。
这类动词主要包括：make, consider, believe, cause, feel, hear, listen to, see, find, have, let, call等。
其句型为：及物动词+宾语+宾语补足语。
（2）名词、形容词、副词、介词短语、不定式、现在分词、过去分词、从句可作宾语补足语。
例如：We all called him “monkey”.（宾补为名词）We believed him honest.（宾补为形容词）I saw him out with his father.（宾补为副词）We found everything in the lab in good order.（宾补为介词短语）I don’t force him to do anything.（宾补为不定式）Nobody noticed him enter the room.（宾补为不带to的不定式）I saw him crossing the road by himself.（宾补为现在分词）When we arrived there, we saw the work done.（宾补为过去分词）【注意】有的动词后若用不定式作其“宾补”则需要省略to。
这类动词有：make，let，have，see，feel，hear，watch，notice，listen to，look at等。
如：I listened to them sing yesterday evening．Ling Feng made the baby laugh．7．表语：用于说明主语的身份、特征或感受，一般由名词、数词、形容词、分词等充当。
常用的连系动词有：be，look，get，sound（听起来），feel，become，smell，turn，taste（尝起来）等。
如：They are workers.（名词）The story is very interesting.（形容）She is at home．（介词短语）Two and three is five．（数词）M y job（工作）is teaching English．（动名词）I feel terrible．（形容词）The dish tastes delicious．（形容词）8、同位语：同位语是在名词或代词之后并列名词或代词对前者加以说明的成分，近乎于后置定语。