just是系动词吗

不是。

adv. 只是，仅仅刚才，刚刚正好，恰好实在刚要

adj. 公正的，合理的正直的，正义的正确的公平的应得的It was just an ordinary day.

那只是普普通通的一天。

The chemistry just wasn't right.

他俩就是擦不出火花。

You're just being paranoid.

你只是在疑神疑鬼。

The child had just wakened.

这孩子刚醒。

Maybe they've just gone shopping.

或许他们刚刚去买东西了。

I've just discovered hang-gliding!

我刚知道有悬挂式滑翔运动！