1、英语句子成份划分英语句子成份划分Members of a Sentence第1页 什么叫句子成份呢?句子组成成份叫句什么叫句子成份呢?句子组成成份叫句子成份。在句子中,词与词之间有一定组子成份。在句子中,词与词之间有一定组合关系,按照不一样关系,能够把句子分合关系,按照不一样关系,能够把句子分为不一样组成成份。句子成份由词或词组为不一样组成成份。句子成份由词或词组充当。充当。当代汉语里普通句子成份有六种,即主当代汉语里普通句子成份有六种,即主语、谓语、宾语、定语、状语和补语。语、谓语、宾语、定语、状语和补语。英语基本成份有七种:主语英语基本成份有七种:主语(subject)、谓语()、谓语(p
2、redicate)、表语)、表语(predicative)、宾语()、宾语(object)、定语)、定语(attribute)、状语)、状语(adverbial)和补语和补语(complement)。)。第2页 英语句子基本结构能够归纳成五种基英语句子基本结构能够归纳成五种基本句型,掌握这五种基本句型,是掌握各本句型,掌握这五种基本句型,是掌握各种英语句子结构基础。种英语句子结构基础。英语英语五种五种基本句型列式以下:基本句型列式以下:一:一:(主谓)(主谓)二:二:(主系表)(主系表)三:三:(主谓宾)(主谓宾)四:四:(主谓间宾直宾)(主谓间宾直宾)五:五:(主谓宾宾补)(主谓宾宾补)第3
3、页基本句型基本句型 一:一:(主谓)(主谓)主语主语:能够作主语成份有:能够作主语成份有名词名词(如(如boy),),主格代词主格代词(如(如you),),动词不定式,动名词动词不定式,动名词等。主语普通在等。主语普通在句首句首。注意名词单数形式。注意名词单数形式常和冠词不分家!常和冠词不分家!谓语谓语:谓语由动词组成,是英语时态、语:谓语由动词组成,是英语时态、语态改变主角,普通在主语之后。态改变主角,普通在主语之后。不及物动不及物动词(词(vi.)没有宾语,形成主谓结构,如:没有宾语,形成主谓结构,如:We come.此句型句子有一个此句型句子有一个共同特点共同特点,即句子谓语,即句子谓语
4、动词都能表示完整意思。这类动词叫做动词都能表示完整意思。这类动词叫做不不及物动词及物动词,后面能够跟,后面能够跟副词、介词短语、副词、介词短语、状语从句状语从句等。等。第4页 (不及物动词)(不及物动词)1.The sun was shining.太阳在照耀着。太阳在照耀着。2.The moon rose.月亮升起了。月亮升起了。3.The universe remains.宇宙长存。宇宙长存。4.We all breathe,eat,and drink.我们大家都呼吸、吃和喝。我们大家都呼吸、吃和喝。5.Who cares?管它呢?管它呢?6.What he said does not ma
5、tter.他所讲没有什么关系。他所讲没有什么关系。7.They talked for half an hour.他们谈了半个小时。他们谈了半个小时。8.The pen writes smoothly 这支笔书写流利。这支笔书写流利。第5页基本句型基本句型 二:二:(主系表)(主系表)此句型句子有一个此句型句子有一个共同特点共同特点:句子:句子谓语动谓语动词词都不能表示一个完整意思都不能表示一个完整意思,必须加上一,必须加上一个表明主语身份或状态个表明主语身份或状态表语表语组成复合谓语,组成复合谓语,才能表示完整意思。这类动词叫做才能表示完整意思。这类动词叫做连系动连系动词词。系动词系动词分两类
6、:分两类:be,look,keep,seem等属一类,表示等属一类,表示情况情况;get,grow,become,turn等属另一类,表示等属另一类,表示改变改变。be 本身没有什么意义本身没有什么意义,只起连系主语和表语作只起连系主语和表语作用。其它系动词仍保持其部分词义。用。其它系动词仍保持其部分词义。感官感官动词多可用作联络动词动词多可用作联络动词:look well/面色好面色好,sound nice/听起来不错听起来不错,feel good/感觉感觉好,好,smell bad/难闻难闻第6页(是系动词)(是系动词)1.This is an English-Chinese dictio
7、nary.这是本英汉辞典。这是本英汉辞典。2.The dinner smells good.午餐气味很好。午餐气味很好。3.He fell in love.他堕入了情网。他堕入了情网。4.Everything looks different.一切看来都不一样了。一切看来都不一样了。5.He is growing tall and strong.他长得又高又壮他长得又高又壮6.The trouble is that they are short of money.麻烦是他们缺乏钱。麻烦是他们缺乏钱。第7页基本句型基本句型 三:三:(主谓宾)(主谓宾)此句型句子此句型句子共同特点共同特点是:谓语动
8、词都含有是:谓语动词都含有实义实义,都是,都是主语产生动作,但不能表示完主语产生动作,但不能表示完整意思整意思,必须跟有一个,必须跟有一个宾语宾语,即动作承受,即动作承受者,才能使意思完整。这类动词叫做者,才能使意思完整。这类动词叫做及物及物动词动词。宾语位于及物动词之后,普通。宾语位于及物动词之后,普通同主同主语组成一样语组成一样,不一样是组成宾语代词必须,不一样是组成宾语代词必须是是代词宾格代词宾格,如:,如:me,him,them等等 第8页(及物动词)(及物动词)1.Who knows the answer?谁知道答案谁知道答案?2.She smiled her thanks.她微笑表
9、示她微笑表示感激。感激。3.He enjoys reading.他喜欢看书。他喜欢看书。4.They ate what was left over.他们吃了剩饭。他们吃了剩饭。5.He said Good morning.他说:他说:早上好!早上好!第9页基本句型基本句型 四:四:(主谓间宾直宾)(主谓间宾直宾)有些及物动词能够有有些及物动词能够有两个宾语两个宾语,如:,如:give给,给,pass递,递,bring带,带,show显示显示。这两。这两个宾语通常一个指个宾语通常一个指人人,为,为间接宾语间接宾语;一个;一个指指物物,为,为直接宾语直接宾语。间接宾语普通位于直。间接宾语普通位于直
10、接宾语之前。接宾语之前。普通次序为:普通次序为:动词动词+间接宾语间接宾语+直接宾语直接宾语。如:如:Give me a cup of tea,please.强调间接宾语强调间接宾语次序为:次序为:动词动词+直接宾语直接宾语+介词介词+间接宾语间接宾语。如:。如:Show this house to Mr.Smith.第10页(及物)(及物)(多指人)(多指人)(多指物(多指物)1.She ordered herself a new dress.她给自己定了一套新衣裳。她给自己定了一套新衣裳。2.She cooked her husband a delicious meal.她给丈夫煮了一顿美
11、餐。她给丈夫煮了一顿美餐。3.He brought you a dictionary.他给你带来了一本字典。他给你带来了一本字典。4.He denies her nothing.他对她什么都不拒绝。他对她什么都不拒绝。5.I showed him my pictures.我给他看我照片我给他看我照片6.I gave my car a wash.我洗了我汽车。我洗了我汽车。第11页基本句型基本句型 五:五:(主谓宾宾补)(主谓宾宾补)此句型句子此句型句子共同特点共同特点是:动词即使是及物是:动词即使是及物动词,不过只跟一个宾语还不能表示完整动词,不过只跟一个宾语还不能表示完整意思,必须加上一个意
12、思,必须加上一个补充成份补充成份来补足宾语,来补足宾语,才能使意思完整。才能使意思完整。宾语补足语:位于宾语之后对宾语作出宾语补足语:位于宾语之后对宾语作出说说明明成份。宾语与其补足语有逻辑上主谓关成份。宾语与其补足语有逻辑上主谓关系,它们一起组成系,它们一起组成复合宾语复合宾语。第12页名词名词/代词宾格代词宾格+名词名词The war made him a soldier.战争使他成为一名战士战争使他成为一名战士.名词名词/代词宾格代词宾格+形容词形容词New methods make the job easy.新方法使这项工作变得轻松新方法使这项工作变得轻松.名词名词/代词宾格代词宾格+
13、介词短语介词短语I often find him at work.我经常发觉他在工作我经常发觉他在工作.名词名词/代词宾格代词宾格+动词不定式动词不定式The teacher ask the students to close the windows.老师让学生们关上窗户老师让学生们关上窗户.名词名词/代词宾格代词宾格+分词分词I saw a cat running across the road.我看见一只猫跑过了马路我看见一只猫跑过了马路.第13页(及物)(及物)(宾语)(宾语)(宾补)(宾补)1.They appointed him manager.他们任命他当经理。他们任命他当经理。2
14、.They painted the door green.他们把门漆成绿色他们把门漆成绿色3.This set them thinking.这使得他们要细想一想。这使得他们要细想一想。4.They found the house deserted.他们发觉那房子无人居住。他们发觉那房子无人居住。第14页 但惯用英语句子并不都象基本句型这但惯用英语句子并不都象基本句型这么简短,这些句子除了基本句型成份不变么简短,这些句子除了基本句型成份不变外,通常是在这些成份前面或后面增加一外,通常是在这些成份前面或后面增加一些修饰语(些修饰语(modifier)而加以扩大。这些)而加以扩大。这些修饰语能够是单
15、词(主要是形容词、副词修饰语能够是单词(主要是形容词、副词和数词),也能够是各种类型短语(主要和数词),也能够是各种类型短语(主要是介词短语、不定式短语和分词短语)。是介词短语、不定式短语和分词短语)。我们称之为:我们称之为:定语、状语定语、状语第15页一、一、定语:定语:定语是对定语是对名词或代词名词或代词起修饰、限定作用起修饰、限定作用词、词、短语或句子短语或句子,汉语中惯用,汉语中惯用表示。定语通表示。定语通常位于被修饰成份前。若修饰常位于被修饰成份前。若修饰some,any,every,no组成复合不定代词时,(如:组成复合不定代词时,(如:something、nothing);或不定
16、式、分词短语);或不定式、分词短语作定语、从句作定语时,则定语通常作定语、从句作定语时,则定语通常置后置后。副词。副词用作定语时须放在名词之后。用作定语时须放在名词之后。形容词作定语形容词作定语:The little boy needs a blue pen.(little修饰名词修饰名词boy;blue修饰名词修饰名词pen.)/小男小男孩需要一支兰色钢笔。孩需要一支兰色钢笔。Tom is a handsome boy./Tom是个英俊男孩。是个英俊男孩。There is a good boy./有个乖男孩。有个乖男孩。第16页数词作定语相当于形容词:数词作定语相当于形容词:Two boys
17、 need two pens.两个男孩需要两支钢笔。两个男孩需要两支钢笔。There are two boys in the room.房间里有两个男孩。房间里有两个男孩。代词或名词全部格作定语代词或名词全部格作定语:His boy needs Toms pen.他男孩需要他男孩需要Tom钢笔。钢笔。His name is Tom.他名字是汤姆。他名字是汤姆。第17页介词短语作定语介词短语作定语:The boy in the classroom needs a pen of yours.教室里男孩需要你一支钢笔。教室里男孩需要你一支钢笔。The boy in blue is Tom.穿兰色衣服
18、孩子是汤姆。穿兰色衣服孩子是汤姆。名词作定语名词作定语:The boy needs a ball pen.男孩需要一支圆珠笔。男孩需要一支圆珠笔。There is only one ball pen in the pencil box.这铅笔盒里只有一支圆珠笔。这铅笔盒里只有一支圆珠笔。第18页副词作定语副词作定语:The boy there needs a pen.那儿男孩需要一支钢笔。那儿男孩需要一支钢笔。The best boy here is Tom.这里最棒男孩是这里最棒男孩是Tom。不定式作定语不定式作定语:The boy to write this letter needs a
19、pen.写这封信男孩需要一支钢笔。写这封信男孩需要一支钢笔。There is nothing to do today.今天无事要做。今天无事要做。第19页分词(短语)作定语分词(短语)作定语:The smiling boy needs a pen bought by his mother.那个微笑男孩需要一支他妈妈买钢笔。那个微笑男孩需要一支他妈妈买钢笔。The pen bought by her is made in China.她买笔是中国产。她买笔是中国产。There are five boys left.有五个留下男孩。有五个留下男孩。第20页定语从句定语从句:The boy who
20、is reading needs the pen which you bought yesterday.那个在阅读男孩需要你昨天买钢笔。那个在阅读男孩需要你昨天买钢笔。The boy you will know is Tom.你将认识男孩叫汤姆。你将认识男孩叫汤姆。There are five boys who will play the game.参加游戏男孩有五个。参加游戏男孩有五个。第21页二、状语:二、状语:状语修饰状语修饰动词、形容词、副词或全句动词、形容词、副词或全句,说明,说明方式、方式、因果、条件、时间、地点、让步、方向、程度、因果、条件、时间、地点、让步、方向、程度、目标目标
21、等。等。状语在句子中位置很灵活,常见情况为:通常在状语在句子中位置很灵活,常见情况为:通常在句子基本结构之后,强调时放在句首;修饰形容句子基本结构之后,强调时放在句首;修饰形容词或副词时,通常位于被修饰词之前;表示时间、词或副词时,通常位于被修饰词之前;表示时间、地点、目标状语普通位于句子两头,强调时放在地点、目标状语普通位于句子两头,强调时放在句首,地点状语普通须在时间状语之前;一些表句首,地点状语普通须在时间状语之前;一些表示不确定时间(如:示不确定时间(如:often)或程度(如:或程度(如:almost)副词状语通常位于副词状语通常位于be动词、助动词、情动词、助动词、情态动词之后,动
22、词之前态动词之后,动词之前。第22页有时状语在句中某个位置会引发歧义,应有时状语在句中某个位置会引发歧义,应注意。注意。如:如:The boy calls the girl in the classroom.普通了解成普通了解成男孩喊教室里女孩男孩喊教室里女孩(此时(此时in the classroom为为girl定语)定语)也能够了解为也能够了解为男孩在教室里喊女孩男孩在教室里喊女孩(此时(此时in the classroom为地点状语),为地点状语),最好写作最好写作In the classroom,the boy calls the girl.第23页副词(短语)作状语副词(短语)作状语
23、:The boy needs a pen very much.男孩非常需要一支钢笔。(程度状语)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.男孩非常需要他母亲买那支钢笔。(宾语男孩非常需要他母亲买那支钢笔。(宾语较长则状语前置)较长则状语前置)The boy needs a pen now./Now,the boy needs a pen./The boy,now,needs a pen.男孩现在需要一支钢笔。(时间状语)男孩现在需要一支钢笔。(时间状语)第24页介词短语作状语介词短语作状语:In
24、the classroom,the boy needs a pen./在教在教室里,男孩需要一支钢笔。(地点状语)室里,男孩需要一支钢笔。(地点状语)Before his mother,Tom is always a boy./在母在母亲面前亲面前,汤姆总是一个男孩子汤姆总是一个男孩子.(条件状语条件状语)On Sundays,there is no student in the classroom./星期天星期天,教室里没有学生教室里没有学生.(时间状语时间状语)分词(短语)作状语分词(短语)作状语:He sits there,asking for a pen./他坐在那儿要他坐在那儿要一支
25、笔。(表示伴随状态)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,男孩需要一因为不得不完成作业,男孩需要一支笔。(原因状语)支笔。(原因状语)Frightened,he sits there soundlessly./(因为)(因为)受了惊吓,他无声地坐在那儿。(原因状语)受了惊吓,他无声地坐在那儿。(原因状语)第25页不定式作状语:The boy needs a pen to do his homework./男孩需要一支笔写家庭作业。(目状语)To make his dream come t
26、rue,Tom becomes very interested in business./为实现梦想,汤姆变得对商业很有兴趣.名词作状语:Come this way!/走这条路!(方向状语)状语从句:时间状语从句、地点状语从句、原因状语从句、结果状语从句、目状语从句、比较状语从句、让步状语从句、条件状语从句 第26页三、同位语:三、同位语:同位语是在名词或代词之后并列名词或代同位语是在名词或代词之后并列名词或代词,对前者词,对前者加以说明加以说明成份,近乎于后置定成份,近乎于后置定语。如:语。如:We students should study hard./(students是是we同位语,都
27、是指同一批同位语,都是指同一批学生学生)We all are students./(all是是we同位语,同位语,都指一样都指一样我们我们)第27页四、独立成份:四、独立成份:有时句子中会有一些有时句子中会有一些与句子没有语法联络成份与句子没有语法联络成份,称为句子独立成份称为句子独立成份(注意:区分于分词独立结构注意:区分于分词独立结构)。感叹词:感叹词:oh,hello,aha,ah,等。等。必定词必定词yes否定词否定词no称呼语:称呼人用语。称呼语:称呼人用语。插入语:一些句中插入插入语:一些句中插入 I think,I believe,等。等。如如:The story,I think
28、,has never come to the end./我相信我相信,这个故事还远没结束这个故事还远没结束.情态词情态词,表示说话人语气(多作为修饰全句状语)表示说话人语气(多作为修饰全句状语):perhaps可能可能,maybe大约大约,acturely实际上实际上,certainly当然,等。当然,等。第28页五、分词独立结构五、分词独立结构:分词作状语时其分词作状语时其逻辑主语逻辑主语与句子与句子主语一致主语一致!不然不然应有自己逻辑主语,组成份词独立结构应有自己逻辑主语,组成份词独立结构。例:例:错句:错句:Studying hard,your score will go up.正确:
29、正确:(1)Studying hard,you can make your score go up.或或(2)If you study hard,your score will go up.解析:错句中分词解析:错句中分词studying没有自带逻辑主语,没有自带逻辑主语,则其逻辑主语就是句子主语,既则其逻辑主语就是句子主语,既your score.显显然做然做study应是人,不应是应是人,不应是your score(分数)(分数).第29页正确句正确句(1)更正了句子主语更正了句子主语,使其与分词逻辑主语一致使其与分词逻辑主语一致(同同为为you);正确句正确句(2)则使用则使用条件分句条
30、件分句带出带出study主语主语,(不过不过已经不是分词结构了已经不是分词结构了).分词独立结构常省略分词独立结构常省略being,having been.不过不过There being.场所不能省略场所不能省略.如:如:Game(being)over,he went home.He stands there,book(being)in hand.独立结构还可用独立结构还可用with、without引导,作状语或定语。这引导,作状语或定语。这种结构不但能够用分词,还能够用不定式、形容词、介词种结构不但能够用分词,还能够用不定式、形容词、介词短语、副词或名词等。如:短语、副词或名词等。如:Wit
31、h nothing to do,he fell asleep soon./无事可做,他无事可做,他很快就睡着了。很快就睡着了。The teacher came in,with glasses on his nose.老师进来了,戴着一付眼镜。(注意,此句老师进来了,戴着一付眼镜。(注意,此句on his nose不可省略!)不可省略!)第30页句子成份练习题句子成份练习题(一一)(一).指出以下句中主语中心词指出以下句中主语中心词 The teacher with two of his students is walking into the classroom.There is an old
32、 man coming here.The useful dictionary was given by my mother last year.To do todays homework without the teachers help is very difficult.第31页(二二)选出句中谓语中心词选出句中谓语中心词 I dont like the picture on the wall.A.dont B.like C.picture D.wall The days get longer and longer when summer comes.A.get B.longer C.da
33、ys D.summer Do you usually go to school by bus?A.Do B.usually C.go D.bus There will be a meeting at the library this afternoon.A.will be B.meeting C.the library D.afternoon Did the twins have porridge for their breakfast?A.Did B.twins C.have D.breakfast第32页 Tom didnt do his homework yesterday.A.Tom
34、B.didnt C.do D.his homework What I want to tell you is this.A.want B.to tell C.you D.is We had better send for a doctor.A.We B.had C.send D.doctor He is interested in music.A.is B.interested C.in D.music Whom did you give my book to?A.give B.did C.whom D.book第33页(三三)挑出以下句中宾语挑出以下句中宾语 My brother hasnt
35、 done his homework.People all over the world speak English.You must pay good attention to your pronunciation.How many new words did you learn last class?Some of the students in the school want to go swimming,how about you?The old man sitting at the gate said he was ill.They made him monitor of the c
36、lass.Go across the bridge and you will find the museum on the left.You will find it useful after you leave school.They didnt know who Father Christmas really is.第34页(四四)挑出以下句中表语挑出以下句中表语 The old man was feeling very tired.Why is he worried about Jim?The leaves have turned yellow.Soon They all became
37、interested in the subject.She was the first to learn about it.第35页(五五)挑出以下句中定语挑出以下句中定语 They use Mr./Mrs.with the family name.What is your given name?On the third lap are Class 1 and Class 3.I am afraid some people forgot to sweep the floor.The man downstairs was trying to sleep.I am waiting for the
38、sound of the other shoe!第36页(六)挑出以下句中宾语补足语 She likes the children to read newspapers and books in the reading-room.He asked her to take the boy out of school.She found it difficult to do the work.They call me Lily sometimes.I saw Mr.Wang get on the bus.Did you see Li Ming playing football on the pla
39、yground just now?第37页(七七)挑出以下句中状语挑出以下句中状语 There was a big smile on her face.Every night he heard the noise upstairs.He began to learn English when he was eleven.The man on the motorbike was traveling too fast.With the medicine box under her arm,Miss Li hurried off.She loves the library because she l
40、oves books.I am afraid that if youve lost it,you must pay for it.The students followed Uncle Wang to see the other machine.第38页(八)划出句中直接宾语和间接宾语 Please tell us a story.My father bought a new bike for me last week.Mr.Li is going to teach us history next term.Here is a pen.Give it to Tom.Did he leave a
41、ny message for me?第39页句子成份练习题句子成份练习题(三三)A1、_ six years since I began to study English.A.It is B.I have been C.There are D.It was 2、_ in the room at that time.A.Nobody was B.Someone were C.Who is D.He are 3、ITS very noisy outside._ is going on?A.Who B.What C.Which D.Where 4、_ in English in class ever
42、y day is important.A.Speak B.Talking C.Saying D.To tell5、There must be_ near the factory.A.a book store B.book store C.books store D.books stores6、Although its raining hard,_ are still working in the fields.A.but they B.and they C.they D.since they第40页B1、The doctor as well as the nurses _ great conc
43、ern for the patients.A.show B.shows C.have shown D.are showing 2、Your son must be a clever boy,_ he?A.is B.isnt C.must D.mustnt 3、The computer center,_ last year,is very popular among students in this school.A.open B.opening C.opened D.being opened 4、I _ go to the shop today,for there is a lot of fo
44、od at home.A.mustnt B.had to C.cant D.neednt 5、Dont _ excited.A.get B.is C.seem D.look 6 This room _ every morning.A.is cleaning B.is cleaned C.cleans D.cleaning 第41页C1、Glad to meet you!_ is your full name?A.What B.Where C.How D.Who 2、He is _ to lift the heavy box.A.too weak B.weak tooC.enough weak
45、D.weak enough3、The days are _ warmer and warmer in spring.A.getting B.looking C.seeming D.going 4、His job is_English.A.teach B.to teach C.taught D.teaches 5、Two balls are_.A.under the desk B.in the wall C.to here D.at desks第42页D1、We should get ready_ others.A.helping B.to help C.help D.help with 2、_
46、interesting work we are doing?A.What a B.How C.What D.What an 3、I want_ a teacher when I grow up.A.to be B.to C.be D.being 4、-Would you like to go on a picnic with me today?-I dont think so.To be honest,I really dont feel like_on apicnic.A.going B.to go C.go D.went 5 Do you know_?A.where does he liv
47、e B.where he livesC.where he live D.if where he lives 6 Let _ do it again.A.I B.me C.he D.she 7 I dont know_.A.how to do B.what to do C.where to do D.when to do 第43页E 1、I saw him _ basketball with Jack an hour ago.A.plays B.to play C.played D.play 2、Sorry,weve kept you_ for a long time.A.waited B.si
48、ng C.stand D.waiting 3、The teacher told us _ late again.A.arent be B.dont be C.not to be D.not be 4、We find the room very_.A.warm B.warmly C.terribly D.hardly第44页F1、I found _ difficult to work together with him.A.it B.its C.that D.those 2、We all know _ our duty to clean our classroom after school ev
49、ery day.A.that B.this C.which D.it 3、He found _ very interesting to play with the little dog.A.what B.it C./D.thatG()1 Tom said he _ a good dream yesterday evening.A.dream B.dreamed C.have D.has()2 Children _ a happy life in China.A.lead B.living C.has D.leading第45页H()1 America,Japan and Canada are_
50、countries.A.developing B.developed C.less developed D.develop()2-_ skirt is that on the chair?-Let me see.Oh,no,its not mine.A.Whose B.What C.Whos D.Which()3 Do you have anything _?A.saying B.to say C.said D.say()4 Look,there is an_tree by the wall.A.apple B.apples C.apples D.apples()5 Where is_seat