脳

1. Origins, structure, and basic meaning

• Structure: 脳 (のう) is a noun for the brain, the organ involved in processing information and bodily functions.
• Basic usage: It appears in an explanation of the brain's function or a figurative feeling that one's brain is tired after difficult thinking.
  • 脳は多くの情報を処理する重要な器官だ。 — The brain is an important organ that processes large amounts of information.
  • 難しい問題を解いた後は、脳が疲れたように感じた。 — After solving the difficult problem, my brain felt tired.

2. Common pitfalls and similar expressions

• Organ and figurative feeling
  • The first example describes the physical organ, while 脳が疲れたように感じた expresses mental fatigue after sustained thinking.