主语
句子一般要有主语。在简单句中，主语一般由名词、代词、动名词或动词不定式(短语) 来充当。动名词、动词不定式作主语时通常用 it 作形式主语。
一：名词
English is very important. 英语是很重要的。
The students all love their English teacher. 这些学生都爱他们的英语老师。A mooncake is a delicious,round cake. The first truck is carrying a few baskets. The temperature will stay above zero.
The doctor looked over Mrs. Brown very carefully. China does not want to copy the USA?s example.
二：代词
They go to school by bus. 他们乘公共汽车上学。
Most of the students come from the countryside. 大多数学生来自农村。 It?s a young forest.
I don?t know if it will grow. That?s a bit expensive.
三：动名词
Watching TV too much is bad for your eyes. 看电视太多对你的眼睛是有害的。no use regretting it. 后悔是无用的。
四：数词 例如:One and two is three.
?s ItOne is not enough for me. I want one more. One of them is English.
Suddenly one of the bags fell off the truck. Two will be enough.
五：动词不定式(短语) (常以 It?s adj. to do sth. 形式出现) To see is to believe. 眼见为实。
It is very hard to get to sleep. 入睡很难。
To give is better than to receive =Its better to give. I found it difficult to get to sleep. It?s glad to see you again. It was difficult to say. But it?s good to swim in summer. 六IT 作主语 1)指代刚刚提到的事物:What?s this? It?s a bus. (指代what)
2)指代一个你不知道或判断不清性别的人:Who?s knocking the door? It?s me. (who)
Who?s the baby in the picture? It?s my sister. (指代 who) 3) 表示时间，天气，距离:
What?s the time? It?s eight o?clock. (时间)
What?s it going to be tomorrow? It?s going to be rainy.(天气) How far is it? It?s about one kilometre away. (距离) 七( THERE 引起的There be 句型中，be 作谓语，主语位居其后。 There are many different kinds of mooncakes. There will be a strong wind.
指代
谓语
谓语必须由动词充当，但动词不定式、动名词、分词为非谓语动词不能作谓语。可作谓语的动词一般为行为动词(表动作)和连系动词(表状态)，行为动词根据其后是否可直接接宾语，又可分为及物动词和不及物动词。
一：及物动词作谓语
We should help each other. 我们应该互相帮助。 They respect one another. 他们互相尊重(对方)。
All of the students like the novel. 所有这些学生都喜欢这本小说。 3
Did you see many people there? 你在那儿看见许多人了吗 二：不及物动词作谓语 He left here yesterday. 他昨天离开这儿。 You?re driving too fast. 你开车开得太快了。
The teacher came in, book in hand. 老师走进教室，手里拿着书。 He went abroad in the September of 1988. 他于1988年9月出国。
三：连系动词表状态
He is an excellent teacher. 他是位优秀的教师。 Her son is a friend of ours. 她的儿子是我们的朋友。 Ours is a great country. 我们的国家是一个伟大的国家。 The box itself is not so heavy. 箱子本身并不重。
谓语 [predicate verb] 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， 繁简程度可把谓语分为简单谓语和复合谓语两类 一：简单谓语。
不论何种时态，语态，语气，凡由一个动词(或动词词组)构成的谓语都是简单谓语。 谓语动词一般由动词的各种时态来体现。例如: I (like) walking.我喜欢走路。(一般现在时主动语态)
I ( made) your birthday cake last night..昨晚我做好了你的生日蛋糕。 (一般过去时主动语态)
It (is used )by travelers and business people all over the world .全世界旅行者和商人都使用它 (一般现在时被动语态)
二：复合谓语 可分为两种情况:
第一种是由情态动词，助动词+不带to的动词不定式构成的重复谓语:
What does this word mean? 这个单词是什么意思, I won’t do it again. 我不会再做它。 I’ll go and move away the bag 我会移走这袋米的。 You’d better catch a bus. 你最好乘坐公交车。
第二种是由连系动词+表语构成的复合谓语。 You look the same. 你(们)看起来一样. We are all go home ，我们回家吧。
My pen is in my bag. 我的钢笔在我的书包里。 I fell tired all the time. 我整天感到疲惫.
He seemed rather tired last night. 他昨天看起来相当的累. 连系动词和表语在意思上紧密联系，不宜分割。
情态动词数量不多,但用途广泛,主要有下列:
can (could), may (might), must, need, ought to, dare (dared), shall (should), will (would) .
情态动词的位置: 情态动词在句中放在谓语动词之前, 谓语动词前若有助动词,则在助动词之前,疑问句中, 情态动词则在主语之前。
英语中助动词有哪些
(1) am,is,are ,was ,were,（帮助变进行时态,帮助变被动语态） (2) do ,does,did （帮助句子变疑问句,否定句,强调谓语动词作用） (3)has ,have （帮助句子变现在完成时态作用）
(4) had ,（帮助句子变过去完成时态,以及虚拟语气倒装） (5) will ,shall （帮助句子变一般将来时态） (6) would ,should （帮助句子变过去将来时态） (7) be going to（帮助句子变一般将来时态）
谓语的辨别 谓语动词和非谓语动词的区别 1) 谓语动词在句中可单独作谓语，而非谓语动词不能单独作谓语。 Miss Mary teaches us English. 玛丽教我们英语。(teaches 动词作谓语) Mr.Victor came to our classroom to have a talk with us last week. 维克托先生上周来到了我们教室和我们谈话。 (to have a talk.... 不定式作状语) 2) 谓语动词受主语的人称和数的限制，而非谓语动词形式没有这种限制。 Larke likes the pop music. 拉克喜欢流行音乐。 (动词用单数第三人称形式) Larke has nothing to do today. 拉克今天没什么事要做。(do 用原形) 3)非谓语动词的特征:如果非谓语动词是及物动词，后面须跟宾语。 Studying English is my favorite. 学习英语是我的爱好。(studying 后跟宾语) 2 非谓语动词可以带有自己的状语或逻辑主语。 Working under such a condition is terrible. 在这样的环境下工作太可怕了。(under such a condition 是 working 的状语) It's too difficult for him to master English in such a short time. 他在这么短的时间内掌握英语太难了。(for him 作不定式的逻辑主语) 3 非谓语动词仍有语态和时态的变化。 I am