Translation of "Essence" in Chinese

The essence of liberty is mathematics.

自由的本质就是数学。

The essence of mathematics is liberty.

数学的本质，是自由。

That is the essence of the matter.

这就是事情的本质。

It's really unfortunate. You don't understand at all its essence.

太可惜了，你一点也不懂它的真髓。

Time is of the essence, Paul. If you don't tell her how you feel now, you'll never have another chance.

時間就是生命，保羅。如果你不告訴她你現在的感覺，你永遠不會有第二次機會。