一旦你做出这个决定，就要意识到它的不可逆性。

Once you make this decision, be aware of its ___irreversibility.

热力学第二定律解释了为什么某些过程的不可逆性是自然界的基本规律。

The second law of thermodynamics explains why the ___irreversibility of some processes is a fundamental law of nature.

手术的不可逆性意味着一旦开始就无法回头。

The ___irreversibility of the surgery means there's no turning back once it begins.