的理论

…'s theory

→ 的
phrase Uncommon #12,887
…'s theory 的 links a possessor or description to 理论 (“theory”). Depending on the context, it can also mean “the theory of/about …”.
CH: 这是我的理论。
EN: This is my theory.

他的理论很难懂。

His theory is very difficult to understand.

我无意争辩你的理论。

I have no intention of arguing with your theory.

我不想听你的理论。

I don't want to hear your theories.

再说一件不怕你挑战的理论

Here’s another theory I’m not afraid to have you challenge.

— 海角七号 (2008)

我要教没人梦想过的理论但只要知道它能用来做什么…就无法回头

I'm going to teach a theory no one has ever dreamed of, but once you know what it can be used for... there's no turning back.

— 奥本海默 (2023)

但我想用它来测试我研究的理论

But I want to use it to test the theory I'm researching.

— 奥本海默 (2023)

实验证明了他的理论。

The experiment proved his theory.

然而,相反的理论往往也是真的。

However, the opposite theory is often true as well.

他有个关于男人迷恋“那话儿”尺寸的理论

He has a theory about men’s obsession with penis size.

— 泰坦尼克号 (1997)