be动词什么时间是连系动词

系动词be

作为系动词（也叫连系动词，link verb）的be，其基本含义为“是”，基本用法结构为“主语+be+表语”，也就是常说的主系表结构，其中的表语一般都由名词、形容词、数词或表地点、时间等的短语来充当。 系动词be有各种时态的变化，也会和情态动词连用。

1、be的时态变化 系动词be会有一般现在时、一般过去时、一般将来时、现在完成时、过去完成时等的时态变化。

如：

He is a student.

They were in 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.

2、be与情态动词的连用 其用法为：情态动词+系动词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