二者時(shí)態(tài)不同，is是一般現(xiàn)在時(shí)態(tài)，was是過(guò)去時(shí)態(tài)。二者用法不同，“現(xiàn)在時(shí)間”用is，“過(guò)去時(shí)間”用was。be動(dòng)詞的形式有am，is，are，been，being，was，were。

be動(dòng)詞

be（be/is/are/am/was/were)[bi:]vi

he is, we are, you are, they are （縮略式 I'm, you're, he's, we're, you're, they're）, （否定縮略式 I'm not, isn't, aren't）, 過(guò)去時(shí) I was, you were, he was, we were, you were, they were （過(guò)去時(shí)否定縮略式 wasn't, weren't）,過(guò)去分詞been,現(xiàn)在分詞being

“Be”除了原形的“be”之外，還有另外七種形式：am, is, are, been, being, was, were.

在句子中，“be”可以是主動(dòng)詞(The Principal Verb)或助動(dòng)詞(The Auxiliary Verb)

例句對(duì)照

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?