其基本含義為“是”,基本用法結(jié)構(gòu)為“主語+be+表語”,也就是我們常說的主系表結(jié)構(gòu),其中的表語一般都由名詞、形容詞、數(shù)詞或表地點、時間等的短語來充當(dāng)。 系動詞be有各種時態(tài)的變化,也會和情態(tài)動詞連用。

(一)be的時態(tài)變化

系動詞be會有一般現(xiàn)在時、一般過去時、一般將來時、現(xiàn)在完成時、過去完成時等的時態(tài)變化。如：

He isa student.

They werein the park yesterday.

It will be cloudy tomorrow.

He has been ill for six days.

It had been three hours before she left the hat shop.

(二)be與情態(tài)動詞的連用

其用法為：情態(tài)動詞+系動詞be原形。如：

It must be Lucy's book. Her name is on the cover.

It can be very difficult for us to memorize too many words within such a short time.

She should be here on time tomorrow.

系動詞可接哪些詞語作表語：

連系動詞后的表語通常是名詞和形容詞，有時也可以是代詞、數(shù)詞、副詞、介詞短語、不定式、動名詞、從句等。如：

1. 用名詞作表語。如：

Translation is an art. 翻譯是一種藝術(shù)。

Beijing is a beautiful city. 北京是一座美麗的城市。

2. 用形容詞表作語。如：

Traveling is interesting but tiring. 旅行是有趣的，但是使人疲勞。

Every hour and every minute is important. 每一小時，每一分鐘，都很寶貴。