头脑 (tóu nǎo): mind, brains

He is not only clever but also very hardworking, so he can get good grades in every exam.

After thinking all night, he finally cleared his head and decided to give up that unrealistic plan.

In an emergency, keeping a cool head is very important; only then can you make the right judgment.

Although that old scientist is advanced in age, his mind is still agile, and he often puts forward novel ideas.