Meaning
The kanji 脳 (のう) fundamentally means 'brain' or 'cerebrum'. It encompasses not only the physical organ but also extends to abstract concepts like intellect, mind, and the capacity for thought. When discussing intelligence or mental faculties, 脳 often appears in expressions, for example, in 頭脳明晰 (zunō meiseki, 'brilliant mind').
Its etymology is quite illustrative. The left-hand radical is 月. When it appears on the left side of a kanji, this component is actually a variant of 肉, meaning 'flesh' or 'meat'. This 'flesh radical' (often called 'niku-zuki') frequently appears in kanji related to body parts or internal organs, clearly indicating that 脳 is an anatomical term. The right-hand component, 囟, is often associated with the skull or a fontanel (the soft spot on an infant's head). This suggests the cranial cavity where the brain resides. Alternatively, some etymological analyses connect it to the idea of a 'springing forth' or 'complex structure' within the head. Together, the components visually convey a 'fleshy organ' located within the 'head' or 'skull', which perfectly aligns with its core meaning. The kanji 脳 has a stroke count of 12 and is typically taught to students in the 6th grade of Japanese elementary school.
Readings
On'yomi (音読み) — Chinese-derived readings
The on'yomi of 脳 is derived from ancient Chinese pronunciation. For 脳, there is one primary and widely used on'yomi reading.
- ノウ (nō)
This is the primary and most common reading for 脳, especially when it appears in compound words or as a standalone noun in formal or scientific contexts. It is used extensively across medical, scientific, and everyday language related to the brain and intellect.
- 脳 (nō) — brain (often used in medical or scientific contexts, or as a general term)
- 頭脳 (zunō) — brain, intellect, gray matter. This compound literally combines 'head' (頭) and 'brain' (脳) to emphasize mental capacity.
- 脳科学 (nōkagaku) — neuroscience. The study of the brain.
- 脳裏 (nōri) — mind, in one's head, inner thoughts. This refers to the inner workings or landscape of the mind.
- 大脳 (dainō) — cerebrum. The largest part of the brain.
- 脳震盪 (nōshintō) — concussion. A common medical term for brain injury caused by impact.
Kun'yomi (訓読み) — Native Japanese readings
Unlike many kanji, 脳 does not have any commonly used kun'yomi (native Japanese readings) when it appears as a single character or in common words. It is predominantly used with its on'yomi reading, ノウ, especially in modern Japanese. This is typical for kanji that represent scientific or medical concepts, or those whose Chinese pronunciation was already established as the standard term upon their introduction to Japan.
Common Words & Compounds
The kanji 脳 forms numerous compounds, especially in fields related to medicine, biology, psychology, and general discussions about intelligence and mental states. Here are some key examples, categorized by theme, to help you understand its versatile usage.
Anatomy and Medical Terms
- 脳 (nō) — brain; The core meaning, often used in medical diagnoses or general discussions.
- 大脳 (dainō) — cerebrum; The largest and most anterior part of the brain.
- 小脳 (shōnō) — cerebellum; A major part of the brain located at the back of the skull.
- 脳髄 (nōzui) — brain matter; Often refers to the substance of the brain itself, or, more broadly, the brain and spinal cord collectively.
- 脳波 (nōha) — brain waves; Electrical activity in the brain.
- 脳外科 (nōgeka) — neurosurgery; The surgical specialty dealing with the brain and nervous system.
- 脳梗塞 (nōkōsoku) — cerebral infarction, stroke; A serious medical condition caused by a blockage of blood flow to the brain.
- 脳腫瘍 (nōshuyō) — brain tumor; An abnormal growth of cells within the brain.
Intellect and Mental States
- 頭脳 (zunō) — brain, intellect, gray matter; Refers to mental faculties or intelligence.
- 脳裏 (nōri) — mind, in one's thoughts, inner vision; Describes what is happening or appears in one's mind.
- 脳細胞 (nōsaibō) — brain cell, neuron; The fundamental units of the brain.
- 脳死 (nōshi) — brain death; The irreversible cessation of all functions of the entire brain.
- 洗脳 (sennō) — brainwashing; The process of coercing someone into adopting radically different beliefs.
Figurative and Everyday Expressions
- 脳天気 (nōtenki) — carefree, optimistic, simple-minded; A descriptive term for someone who is overly optimistic or lacks worry, sometimes to the point of being naive.
Example Sentences
人間の脳はとても複雑です。
Ningen no nō wa totemo fukuzatsu desu.
The human brain is very complex.
脳を健康に保つために、適切な睡眠が必要です。
Nō o kenkō ni tamotsu tame ni, tekisetsu na suimin ga hitsuyō desu.
Adequate sleep is necessary to keep the brain healthy.
彼は頭脳明晰で、いつも的確な判断をします。
Kare wa zunō meiseki de, itsumo tekikaku na handan o shimasu.
He has a brilliant mind and always makes accurate judgments.
脳科学の研究は、日々進歩しています。
Nōkagaku no kenkyū wa, hibi shinpo shiteimasu.
Research in neuroscience is advancing day by day.
その事件が脳裏に焼きついて離れない。
Sono jiken ga nōri ni yakitsuite hanarenai.
That incident is burned into my mind and won't leave me.
怪我により軽い脳震盪を起こした。
Kega ni yori karui nōshintō o okoshita.
He suffered a mild concussion due to the injury.
読書は脳の活性化に良いと言われています。
Dokusho wa nō no kasseika ni yoi to iwareteimasu.
Reading is said to be good for brain activation.
手術は脳外科医によって成功裏に終わった。
Shujutsu wa nōgekai ni yotte seikōri ni owatta.
The surgery was successfully completed by the neurosurgeon.
このパズルは脳を使うので、とても楽しいです。
Kono pazuru wa nō o tsukau node, totemo tanoshī desu.
This puzzle uses your brain, so it's a lot of fun.
彼は少々脳天気な性格だが、皆に愛されている。
Kare wa shōshō nōtenki na seikaku da ga, mina ni aisareteiru.
He has a somewhat carefree personality, but everyone loves him.
Memory Tip
To remember 脳, think of its two main components. On the left, we have 月, which in this context is the 'flesh' radical (肉), indicating a body part. Imagine this as the fleshy mass of the brain itself. On the right, we have a more complex component. You can visualize this part as a representation of the 'skull' or the 'complex folds' of the brain. Perhaps it even abstractly resembles thoughts or ideas flowing within it. A simple mnemonic could be: "The fleshy (月) organ in your head (the right part representing the skull/brain structure) that allows you to think is your brain." Focus on the flesh radical signifying a biological organ, and the right side as the intricate container or essence of thought, making the connection to 'brain' very strong.