名词通常作主语,宾语,表语或同位语.宾语中又可作动宾和介宾.
例句：作主语 Water is important to us.这里的water就是作主语.
作动宾 I like apples.
作介宾 I go to school by bike.这里的to是介词,school作to的宾语.
作表语 The most important thing in pur life is honesty.这里的honesty作be动词的表语
作同位语 Shanghai,a modern city,is located in the east of China.这里的city作Shanghai的同位语（解释说明作用）
形容词通常作定语,表语或补语.
例句：作定语 I have a beautiful dress.这里的beautiful作dress的定语修饰它.
作表语 My house are big.这里的big作be动词表语修饰house.
作主语补语 He died poor.这里的poor可看作与主语He是系表结构,可理解为：He was poor when he died.他死的时候很穷.
作宾语补足语 Tom painted the wall red.这里的red作paint的补语,可看作与宾语wall是系表结构,可理解为Tom painted the wall and the wall was red.汤姆把墙刷成了红色.
副词通常用来修饰形容词或动词,甚至一句句子.
She is quite happy.quite修饰happy.表示程度深.
Bob runs fast.fast修饰run.
Unfortunately,Peter's grandpa passed away yesterday.这里的unfortunately修饰整句句子.
动词作句子中的谓语,或者成为非谓语中的一部分.
谓语这块我就不再赘述了,非谓语比较烦,但主要就三大类,动名词,不定式和分词.
动名词,它和名词的功能类似,就是V+ing形式,名词的作用他基本都能具备.
不定式,to do结构,可在句中充当许多作用,作名词,形容词,副词（状语）功能等等
分词,有过去分词和现在分词两种,过去分词为动词的完成时态,现在分词为动词的进行时态,但他们都不能作句子的主语和谓语,只能作表语,定语,补语或状语.
I love drawing.（动名词作宾语）
Seeing is believing（动名词作主语和宾语）
lt is impossible for me to finish the work in two days.（不定式主语）
My ambition is to be a teacher.(不定式作表语)
Have you got a key to unlock the door.(不定式作形容词功能修饰key)
I sit by the window,enjoying the sunshine.(分词作状语)
The movie is inspiring.(分词表语)
the risen sun(分词作定语)
I saw the children playing a game.(分词作宾语补足语)
介词后面通常只能接名词,代词和动名词.
例句：I live in Beijing.
介词还有一个功能就是和不及物动词结合,形成了及物动词形式.
例句：Look at the picture.look是不及物动词,与at是固定搭配,构成了一个表示动作的及物动词形式.类似的还有listen to,think about/of等等
代词的用法就是指代一个名词,与名词的作用一样.
例句：It is a dog.