positively

区别不大，很多意思相近，但是有固定搭配，通过例举理解用法

indeed

adv. 的确；实在；真正地；甚至

Later, he admitted that the payments had indeed been made.

后来，他承认说的确是付过款了。

"Did you know him?"—"I did indeed."

“你认识他吗？”—“我确实认识他。”

surely

adv. 当然，肯定，无疑；坚定地；稳当地

You're an intelligent woman, surely you realize by now that I'm helping you.

你是个聪明的女人，你现在肯定意识到我在帮你。

He knew that under the surgeon's knife he would surely die.

他知道在这位外科医生的刀下他会必死无疑。

certainly

adv. 当然；行（用于回答）；必定

"In any case you remained friends."—"Certainly."

“不管怎样，你们还是朋友。”—“那当然。”

The public is certainly getting tired of hearing about it.

公众无疑厌倦了听这方面的事。

truly

adv. 真实地，不假；真诚地

a truly democratic system.

一个真正民主的体制。

positively

adv. 肯定地；明确地；断然地

This is positively the last chance for the industry to establish such a system.

这绝对是该行业建立此机制的最后一次机会。

absolutely

adv. 绝对地；完全地

Joan is absolutely right.

琼绝对正确。

I absolutely refuse to get married.

我绝对拒绝结婚。

really

adv. 实际上，事实上；真正地，真实地；非常

My father didn't really love her.

我父亲实际上并不爱她。

It was really good.

这非常好。