be動(dòng)詞用法：
當(dāng)做主動(dòng)詞時(shí)，“be”在性質(zhì)上屬于接系動(dòng)詞(The Linking Verb), 后面要有名詞、形容詞、地方副詞或短語(yǔ)作補(bǔ)足語(yǔ)(The Complement)。例如：
The man is a science teacher.
這個(gè)男子是一位科學(xué)教師。
Mary's new dresses are colourful.
瑪麗的新衣服色彩鮮艷。
I have been there before.
我以前去過(guò)那里。
My mother is in the kitchen now.
我媽媽現(xiàn)在在廚房里。
這四個(gè)都是陳述句，可以變成疑問(wèn)句，方法簡(jiǎn)單，把主語(yǔ)和“be”或助動(dòng)詞對(duì)換位置即可：
Is the man a science teacher?
Are Mary's new dresses colourful?
Have I been there before?
Is mother in the kitchen now?
當(dāng)“be”要在祈使句中出現(xiàn)時(shí)，陳述句可借助助動(dòng)詞“do”，否定句必須在前加上助動(dòng)詞“don't”，如：
Don't be silly!
Do be obedient!
Be careful!
Don't be a fool!
“Be”有兩種縮寫(xiě)法，如下：
He's not...../He isn't....
You're not...../You aren't...
但“am + not”的縮寫(xiě)法只有一個(gè)：
I'm not.