Act on/upon

对…起作用；按照…行事

The medicine doesn’t act on his illness.

这种药对他的病没有作用。

You’d better act on my suggestion.

你最好照我的建议去做。

I don’t agree his plan, but I have to act upon his order.

我不同意他的计划，但我必须按照他的命令行事。



Act out

把…表演出来；因（压抑等）发泄出来

The two children acted out the fairy tale.

这两个孩子表演了童话故事。

I won’t blame him. I know he’s just acting out.

我不会怪他的。我知道他只是在发泄他压抑的情绪。



Act up

调皮；运作不正常; （身体某部分）疼痛起来

How long has your head been acting up?

你的头痛了多久了？

His old Jeep acted up again.

他的旧吉普车又出毛病了。

Because I didn’t give her my cell phone, my niece started acting up.

因为我没把手机给她，我侄女开始调皮捣蛋起来。



Act for

代理(某人职务)，代办

He asked his assistant to act for him in this matter.

他叫他的助理代他处理这件事。

As the manager was ill, our boss asked me to act for him.

由于经理病了，老板要求我代替他的职位。



Act as

充当，用作；扮演…的角色

The doctor said that insomnia might act as a trigger for his illness.

医生说失眠可能是引发他的疾病的原因。

I was asked to act as a negotiator at the meeting.

我被要求在会议上担任谈判代表。