一个英语句子到底是怎么样的一个结构?

一．主语：主语(subject) 是一个句子的主题( theme), 是句子所述说的主体.它的位置一般在一句之首.可用作主语的有单词、短语、从句乃至句子.
1．名词作主语. 如：A tree has fallen across the road. (一棵树倒下横在路上.)
Little streams feed big rivers. ( 小河流入大江.)
2．代词用作主语.如：You’re not far wrong. (你差不多对了).
He told a joke but it fell flat. (他说了个笑话,但没有引人发笑
3．数词用作主语.如：Three is enough. 三个就够了.
Four from seven leaves three. 7减4余3.
4．名词化的形容词用作主语.
The idle are forced to work. 懒汉被迫劳动.
Old and young marched side by side. 老少并肩而行.
5．副词用作主语.如：Now is the time. 现在是时候了.
Carefully does it. 小心就行.
6．名词化的介词作主语.如：The ups and downs of life must be taken as they come.
我们必须承受人生之沉浮.
7．不定式用作主语. 如：To find your way can be a problem.你能否找到路可能是一个问题.
It would be nice to see him again.
如能见到他,那将是一件愉快的事.
8． 动名词用作主语.如：Smoking is bad for you. 吸烟对你有害.
Watching a film is pleasure, making one is hard work.
看电影是乐事, 制作影片则是苦事.
9． 名词化的过去分词用作主语.如：The disabled are to receive more money.
残疾人将得到更多的救济金.
The deceased died of old age.
死者死于年老.
10. 介词短语用作主语.如：To Beijing is not very far. 到北京不很远.From Yenan to Nanniwan was a three-hour ride on horseback.
从延安到南泥湾要三个小时.
11.从句用作主语.如: Whenever you are ready will be fine.
你无论什么时候准备好都行.
Because Sally wants to leave doesn’t mean that we have to.
不能说萨利要走因而我们也得走.
12.句子用作主语.如：”How do you do ?” is a greeting.“你好”是一句问候语.
二．谓语
谓语(predicate) 或谓语动词(predicate verb) 的位置一般在主语之后.谓语由简单动词或动词短语（助动词或情态动词＋主要动词）构成.
1．由简单的动词构成.
(1). What happened? 发生了什么事?
(2). He worked hard all day today. 他今天苦干了一天.
(3). The plane took off at ten o’clock. 飞机是十点起飞的.
2．由动词短语构成的谓语.
(1). I am reading. 我在看书.
(2). What’s been keeping you all this time? 这半天你在干什么来着?
(3). You can do it if you try hard. 你努力就可以做到.
3．英语常用某些动作名词代替表动态的谓语动词,表生动.这种动作名词之前常用没有多大意义的动词have, get, take, give 等.如：
(1). I had a swim yesterday. 我昨天游了一次水（had a swim 代替了swam）
(2). Take a look at that! 你看看那个!（take a look 代替了 look）
(3). He gave a sigh. 他叹了口气.（gave a sigh 代替了sighed）
(4). I got a good shake-up.我受到了很大的震动.（a good shake-up 代替了was shaken up thoroughly(充分,彻底的)）
三．表语
表语的功能是表述主语的特征、状态、身份等.它也可以说是一种主语补语.它位于联系动词之后,与之构成所谓的系表结构.在系表结构钟,联系动词只是形式上的谓语,二真正起谓语作用的则是表语.可以作表语的词有：名词、代词、数词、形容词、副词、不定式、动名词、分词、介词短语、从句等.
1．The wedding was that Sunday. 婚礼是在那个星期天举行的.（名词）
2．So that’s that. 就是这样.（代词）
3．We are seven. 我们一共7人.（数词）
4．Are you busy? 你有空吗?（形容词）
5．Are you there? 你在听吗?（电话用语）（副词）
Is anybody in? 里面有人吗? （副词）
6．All I could do was to wait. 我只能等待.（不定式）
My answer to his threat（威胁） was to hit him on the nose.
我对他的威胁的回答是照他的鼻子打去.（不定式）
7．Complimenting（赞美,祝贺） is lying. 恭维就是说谎.（动名词）
Is that asking so much? 这是要的高了吗?（动名词）
8．I was so much surprised at it. 我对此事感到很惊讶.（过分）
I’m very pleased with what he has done. 我对他所做的很满意.（过分）
9．She is in good health. 她很健康.（介词短语）
The show is from seven till ten. 演出时间为7点至10点.（介词短语）
10．Is that why you were angry? 这就是你发怒的原因吗?（从句）
11．This is where I first met her. 这就是我初次与她会面的地方.（从句）
补充：
能做系动词的实义动词：
come , go , run, turn ,get , become , keep , stay , make (表变化的动词)
fell,sound ,smell , look , taste （感观动词）
seem, appear (似乎,好像)
例如：
1．Our dream has come true. 我的梦想实现了.（Come后常加 easy ,loose natural 等）
2. He fell sick. 他病了.
Keep fit.保重.
Keep作为系动词还常接quiet ,calm ,cool, well, warm ,silent,clean,dry
3．The well ran dry. 这口井干枯了.（short , loose , wild , cold 等）
4．A thin person always seems to be taller than he really is.
一个瘦个子似乎比他的实际高度要高些.
四．宾语
宾语（object）在句中主要充当动作的承受者,因此一般皆置于及物动词之后.如：
Our team beat all the others. 我们的球队打败了所有其他球队.
可以用作宾语的有：名词、代词、数词、名词化的形容词、副词、不定式、动名词、名词化的分词、从句等.
1．Do you fancy a drink? 你想喝一杯吗?（名词）
2．They won’t hurt us. 他们不会伤害我们.（代词）
3．If you add 5 to 5, you get 10. 5加5等于10.（数词）.
4．I shall do my possible. 我将尽力而为.（名词化形容词）
5．He left there last week. 他上个星期离开了那里.（副词）
6．Does she really mean to leave home? 她真的要离开家吗?（不定式）
7．He never did the unexpected(想不到的,意外的).
他从不做使人感到意外的事.（名词化的分词）
8．Do you understand what I mean? 你明白我的意思吗?（从句）
扩展：
宾语中有些动词需要两个同等的宾语,即直接宾语(direct object)与间接宾语(indirect object).直接宾语一般指动作的承受者,间接宾语指动作所向的或所为的人和物（多指人）,具有这种双宾语的及物动词叫做与格动词(dative verb), 常用的有：answer, bring, buy, do, find, get, give, hand, keep, leave, lend, make, offer, owe, pass, pay, play, promise, read, save, sell, send, show, sing, take 等,间接宾语一般须与直接宾语连用,通常放在直接宾语之前.如：I have found him a place. 我给他找到了一个职位.
五．补语
补语（complement）是一种补足主语和宾语的意义的句子成分.补足主语意义的句子成分叫做主语补语（subject complement）,补足宾语意义的句子成分叫做宾语补语（object complement）.
(1). 容词用作主语补语是常置于主语之前,后有逗号.
Tired and sleepy, I went to bed. 我又累又困,就去睡了.
有时可以置于主语之后,前后都有逗号,与非限定性定语相似.如：
The man, cruel beyond belief, didn’t listen to their pleadings.
那人不可置疑地残酷,不听取他们的恳求.
(2).可以用做宾语补语的有名词、形容词、不定式、动名词、分词、介词短语等
1.They named the child Jimmy. 他们将孩子命名为吉米.（名词用作并与补语）
2.My mother looks so young that you would think her my sister.
我的母亲面很嫩,你会以为她是我的姐姐（名词短语作宾语补语）
3. He boiled the egg hard. 她将鸡蛋煮老了.（形容词用作宾语补语）
3.I found the book very interesting.我发现那本书很有趣.（形容词短语用作宾补）
4.The comrades wanted Dr. Bethune to take cover.
同志们要白求恩大夫隐蔽一下.（不定式用作宾语补语）
5.I call this robbing Peter to pay Paul.我把这个叫做拆东墙补西墙.（动名作宾补
6.Don’t take his kindness for granted.不要把他的友善看作是当然的事.
六．定语
定语是用来说明名词（代词）的品质与特征的词或一组词.可用作定语的有：形容词、名词、代词、数词、副词、不定式、动名词、分词、介词短语、从句和句子等.
1．形容词用作定语是大量的.
（1）. She is a natural musician. 她是一位天生的音乐家.
（2）. He must be the best violinist alive.他一定是最好的在世的小提琴手了.（后置定语）
2. 名词用作定语.如
（1）. A baby girl 女婴
（2）. well water 井水
(3). Sports car 双座轻型汽车
（4）. A fool’s paradise 梦幻的天堂
2．代词作定语.
（1）. Your hair needs cutting. 你该理发了.（物主代词用作定语）
（2）. Everybody’s business is nobody’s business. 人人负责就是无人负责.
（不定代词所有格作定语）
3．数词作定语
（1）. There’s only one way to do it. 做此事只有一法.
（2）. Do it now, you may not get a second chance.
现在就干吧,你可能再没有机会了.
基数词用作后置定语： page 24 Room 201 the year 1949
4. 副词充当定语时常后置,如：
the room above 楼上的房间 the world today 今日世界
the way out 出路 a day off 休息日
5．不定式用作定语
（1）. Her promise to write was forgotten.她忘记了答应写信的事.
（2）. That’s the way to do it.那正是做此事的方法.
6．动名词用作定语.
A walking stick 拐杖 sleeping pills 安眠药
eating implements 吃饭用具 learning method 学习方法
7．分词充当定语
a sleeping child 正在睡中的小孩 a drinking man 嗜酒者
a retired worker 一个退休工人 a faded flower 一朵谢了的花
7．介词短语用作定语.
（1）. This is a map of China. 这是一幅中国地图.
（2）. The wild look in his eyes spoke plainer than words.
他那凶暴的目光说明得再清楚不过了.
8．从句用作定语,即定语从句
The car that’s parked outside is mine. 停在外面的车是我的.
Your car, which I noticed outside, has been hit by another one.
我在外面看见你的汽车了,它给另一辆车撞了.
七．同谓语
当两个指同一事物的句子成分放在同等位置时,一个句子成分可被用来说明或解释另一个句子成分,前者就叫做后者的同谓语（appositive）.这两个句子成分多由名词（代词）担任,同谓语通常皆放在其说明的名词（代词）之后.
1．名词用作同谓语是大量的.
（1）. We have two children, a boy and a girl.我们有两个孩子,一男一女.
（2）We, the Chinese people, are determined to build China into a powerful and prosperous country. 我们中国人民决心将中国建成一个强大的繁荣的国家.
2．代词用作同谓语.
（1）.They all wanted to see him. 他们都想见他.
（2）.Let’s you and me go to work, Oliver. 咱们俩去工作吧.
3．数词用作同谓语.
（1）.Are you two ready?你们俩准备好了吗?
（2）.They two went, we three stayed behind.他们俩去了,我们三个留了下来.
4．不定式与动名词用作同谓语.
（1）.Their latest proposal, to concentrate on primary education, has met with some opposition.他们最近提出了集中全力于初等教育的提议遭到了某些人的反对.
（2）.The first plan, attacking at night, was turned down.
第一个计划是夜袭,被拒绝了.
5．Of 短语用作同谓语
The city of Rome 罗马城 the art of writing 写作艺术
The vice of smoking 吸烟嗜好
6．从句用同谓语,即同谓语重句
（1）.The news that we are having a holiday tomorrow is not true.
明天放假的消息不确.
（2）.We are not investigating the question whether he is trustworthy.
我们不是在调查他是否可信赖的问题.
八．状语
状语（adverbial）是修饰动词、形容词、副词以及全句的句子成分..如：
1．The girl is improving remarkably. 这个女孩大有进步.
2．可用作状语的有副词、名词、代词、数词、形容词、不定式、分词、介词短语、从句等.
（1）.副词最常用作状语,位置比较灵活,可置句末、句首和句中.
He speaks the language badly but read it well.
这种语言,他讲得不好,但阅读能力很强.
Naturally we expect hotel guests to lock their doors.
当我们期望旅馆的旅客把房门锁上.
3．状语按用途来分,可以分为时间、地点、方式、原因、结果、目的、条件、让步、程度、方式、伴随等
（1）.时间状语,多位于句末和句首,有时亦可置于句中
Shall we do the shopping today or tomorrow?
In China now leads the world.
(2).地点状语,多置于句末,有时也位于句首和句中.
There are plenty of fish in the sea.
She kissed her mother on the platform(月台).
（3）.原因状语,包括表理由的状语,多置于句末,有时亦可置于句首.
Because he was ill ,Tom lost his job.
I eat potatoes because I like them.
(4). 结果状语,多由不定式、分词和从句表示,常位于句末.
She woke(醒) suddenly to find someone standing in the doorway.
She spoke so softly that I couldn’t hear what she said.
(5). 目的状语,多由不定式、介词短语和从句等表示,常位于句末,强调时可以置于句首.
He ran for shelter(隐蔽处).他跑去避雨.
In order to get into a good school, I must study even harder.
(6). 条件状语.多由短语和从句表示,常置于句末和句首.
We’ll be lucky to get there before dark.
If he were to come, what should we say to him?
(7). 让步状语,由短语和从句表示,常置于句末和句首.
For all his money, he didn’t seem happy. 他尽管有钱,但似乎并不幸福.
He helped me although he didn’t know me.
(8).程度状语.常由副词、介词短语及从句等表示.
The lecture is very interesting.
To what extent would you trust them? 你对他们信任程度如何?
（9）.伴随状语,常由短语和独立主格等表示.对位于句末和句首.
My train starts at six, arriving at Chicago at ten.
He stood there ,pipe(烟斗) in mouth.

别在这里问，看书去，看了就明白了

最简单的句型是，1.主语+谓语+宾语（如：I love you）2.主语+系动词+表语（如：I am hungry).
至于复杂的句子，只是在这个句型的基础之上添加了定语、状语等成分而已。