简单句就是构成一个句子最简单的结构。复合句也是建立在简单句的基础上，用各种不同的连词把两个简单句子连接起来。简单句核心是动词，就是因为动词的不同衍生出5种基本句型。
动词是系动词就是“主语 系动词 表语”的主系表结构。
China is a great country. China主语 is 联系动词 a great country 为表语。
动词是不及物动词就是“主语 不及物动词”的主谓结构。
The rain stopped. stop为不及物动词，不能带宾语。
动词是及物动词就是“主语 谓语 宾语”的主谓宾结构。
The boy bought a book.
双宾语和复合宾语是建立在主谓宾的基础上。
My parent gave me a new watch on my birthday.
He told me to have a good rest.
通过上面的描述，我们知道动词是句子的核心。一个句子可以没有主语（祈使句），可以没有宾语，但是不能没有谓语。
下面对五种基本句型做详细说明：
1. 主语 谓语
Li Ming works very hard.
李明学习很努力。(Li Ming是主语; works是谓语。)
The accident happened yesterday afternoon.
事故是昨天下午发生的。(The accident是主语; happened是谓语 )
Spring is coming.
春天就要来了。(Spring是主语; is coming是谓语。)
2. 主语 谓语 宾语
Li Lei always helps me when I have difficulties.
当我遇到困难时,李雷总能给我帮助。(Li Lei是主语, helps是谓语,me是宾语。 )
She plans to travel in the coming May Day.
她打算在即将到来的“五一”外出旅游。(She是主语, plans是谓语,to travel是宾语。)
I don’t know what I should do next.
我不知道下一步该干什么。(I是主语; don’t know是谓语, what I should do next是宾语。)
3. 主语 系动词 表语
This kind of food tastes delicious.
这种食物吃起来很可口。(This kind of food是主语, tastes是系动词, delicious是表语。)
He looked worried just now.
刚才他看上去有些焦急。(He是主语, looked是系动词, worried是表语。)
4. 主语 谓语 双宾语
Her father bought her a dictionary as a birthday present.
她爸爸给她买了一本词典作为生日礼物。(Her father是主语, bought是谓语, her是间接宾语, a dictionary是直接宾语。)
The old man always tells the children stories about the heroes in the Long March.
老人经常给孩子们讲述长征途中那些英雄的故事。(The old man是主语,tells是谓语, the children是间接宾语,stories about the heroes是直接宾语。)
上述句子还可以表达为:
Her father bought a dictionary for her as a birthday present.
(Her father是主语, bought是谓语, a dictionary是直接宾语 her是间接宾语。)
The old man always tells stories about the heroes to the children in the Long March.
(The old man是主语,tells是谓语, stories about the heroes是直接宾语,children是间接宾语。)
5. 主语 谓语 宾语 宾语补足语
You should keep the room clean and tidy.
你应该让屋子保持干净整洁。(You是主语, should keep是谓语,the room是宾语,clean and tidy是宾语补足语。)
We made him our monitor.
我们选他当班长。(We是主语,made是谓语,him是宾语,our monitor是宾语补足语。)
His father told him not to play in the street.
他父亲告诉他不要在街上玩。(His father是主语,told是谓语, him是宾语, not to play是宾语补足语。 )
