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B1 noun 10 min read

寝不足

Practice it Examples Notes & Tips 寝不足 in 30 Seconds

Explanation 寝不足 in your Level:

At the A1 level, you should focus on the basic meaning of 'nebusoku' as 'not enough sleep'. You might not use the word itself yet, but you will learn it as a reason for feeling 'nemui' (sleepy). Think of it as a simple label for a common feeling. In A1, you mostly use short sentences like 'Nebusoku desu' (I lack sleep). You learn that 'ne' comes from 'neru' (to sleep). It's a useful word to know when you want to explain to your teacher or friends why you are tired in class. You don't need to worry about complex grammar yet, just remember that it is a noun that describes the state of your body after a short night. It is one of the first 'body state' nouns you might encounter alongside 'onaka ga suita' (hungry) or 'nodo ga kawaita' (thirsty). Even at this basic level, knowing 'nebusoku' helps you move beyond just saying 'I am tired' and gives a specific reason for your tiredness, which is a key step in building your descriptive abilities in Japanese.

At the A2 level, you begin to use 'nebusoku' with simple particles like 'de' to show cause and effect. You can say things like 'Nebusoku de tsukaremashita' (I'm tired because of lack of sleep). You also start to recognize the kanji: 寝 (sleep), 不 (not), and 足 (enough). This level involves understanding that 'nebusoku' is a noun and cannot be used like a verb. You might use it in basic daily diaries or when talking about your weekend. You also learn to differentiate between 'nebusoku' and 'nemui'. While 'nemui' is how you feel right now, 'nebusoku' is the reason why. For example, 'Kinou wa nebusoku deshita. Dakara, kyou wa nemui desu' (Yesterday was a lack of sleep. Therefore, today I am sleepy). This shows a clear grasp of logical connection. You also start to hear the word in basic listening exercises about daily routines and health. It's a very practical word for A2 learners because it appears so often in textbooks and real-life conversations about work and study habits.

At the B1 level, you are expected to use 'nebusoku' fluently in various contexts. You should be able to use it to modify other nouns using 'no', such as 'nebusoku no hi' (a day of insufficient sleep). You also start using the phrase 'nebusoku-gimi' (feeling a bit short on sleep) to add nuance to your speech. At this level, you understand the cultural context of the word in Japan—how it relates to the 'salaryman' culture and the pressure on students. You can participate in longer conversations about health and lifestyle, using 'nebusoku' as a key term. You might say, 'Saikin nebusoku ga tsuzuite ite, nakanaka shigoto ni shuuchuu dekimasen' (Lack of sleep has been continuing lately, and I just can't concentrate on work). This shows you can link multiple ideas and express a persistent state. You also begin to distinguish between 'nebusoku' and the more formal 'suimin-busoku', choosing the appropriate one based on who you are talking to. B1 learners should also be able to read short articles about the dangers of 'nebusoku' and summarize the main points.

At the B2 level, your use of 'nebusoku' becomes more sophisticated. You can discuss the societal implications of chronic 'nebusoku' in Japan, such as its impact on the economy or public safety. You use the word in complex sentence structures, incorporating it into relative clauses and using it with a wider range of particles and auxiliary verbs. For example, 'Nebusoku ga hikio-okosu koushin-shikkan no risuku ni tsuite...' (Regarding the risk of cardiovascular disease caused by lack of sleep...). You are comfortable using 'nebusoku' in both casual and semi-formal settings. You also understand related idioms and more advanced synonyms like 'fumin' (insomnia) or 'jukusui' (deep sleep) and can explain the differences between them. In writing, you can use 'nebusoku' to build a persuasive argument about the importance of work-life balance. Your listening skills allow you to catch the word even when spoken quickly in news broadcasts or natural conversations. You recognize it as a common 'set-up' word in jokes or storytelling in Japanese media.

At the C1 level, you have a deep, nuanced understanding of 'nebusoku'. You can use it in highly formal or academic contexts, perhaps substituting it with 'suimin-busoku' when appropriate for the register. You can discuss the physiological and psychological mechanisms of sleep deprivation using this term as a foundation. You are aware of the subtle social signals sent when someone mentions their 'nebusoku'—is it a genuine cry for help, a humble brag about their hard work, or a simple greeting? You can navigate these social nuances perfectly. In literary contexts, you can appreciate how 'nebusoku' is used to set a mood of exhaustion or desperation. You can also use the word in professional environments to discuss employee wellness programs or safety protocols. Your vocabulary includes related technical terms, and you can explain the etymology of the kanji components in detail. For a C1 learner, 'nebusoku' is not just a word for 'tired'; it's a versatile tool for discussing health, culture, and society at a high level of abstraction.

At the C2 level, 'nebusoku' is a word you master in all its dimensions—linguistic, cultural, and technical. You can engage in expert-level debates about sleep hygiene and public policy, using 'nebusoku' and its formal variants with total precision. You understand the historical evolution of the word and how its usage has changed alongside Japan's economic development. You can interpret the word's appearance in classical or modern literature, analyzing its symbolic weight. Your command of the language allows you to use 'nebusoku' in creative writing to evoke specific, culturally-grounded imagery. You can also provide linguistic analysis of the word, comparing it to similar constructs in other languages. For a C2 speaker, 'nebusoku' is a small but essential part of a vast, interconnected web of knowledge about the Japanese language and the people who speak it. You can switch registers instantly, from a casual 'Nebusoku da wa' with a close friend to a formal 'Suimin-busoku ga kinen-sareru...' in a professional lecture, without a second thought.

Practice it Examples Notes & Tips

寝不足 in 30 Seconds

Nebusoku (寝不足) is a common Japanese noun that translates to 'lack of sleep' or 'insufficient sleep' in English, used in many daily situations.
It is formed from the kanji for sleep (寝) and insufficiency (不足), highlighting a quantitative shortage of rest rather than just a feeling.
Grammatically, it is a noun that often uses the particle 'de' to indicate cause or 'no' to modify other nouns in a sentence.
Culturally, it is a significant word in Japan, often used to explain fatigue in professional and academic settings where long hours are common.

The Japanese term 寝不足 (Nebusoku) is a quintessential part of the Japanese lexicon, especially within the context of a society known for its rigorous work ethic and demanding academic environment. At its most fundamental level, the word is a compound noun formed by two distinct parts: 寝 (Ne), which is the stem of the verb neru (to sleep), and 不足 (Busoku), which means insufficiency, shortage, or lack. When combined, they describe a physical and mental state resulting from not having obtained an adequate amount of sleep. It is important to distinguish this from simply being 'sleepy' (眠い - nemui). While 'nemui' is a temporary feeling of drowsiness, 'nebusoku' refers to the underlying condition or the cause of that drowsiness. In the Japanese cultural landscape, admitting to 'nebusoku' is often more than just a health complaint; it can be a subtle signal of one's dedication to work or study, though in modern health-conscious circles, it is increasingly viewed as a lifestyle issue to be corrected.

Grammatical Category: Noun (Meishi). It can also function as a No-adjective (nebusoku no) or be used with the copula 'da/desu'.

Common Contexts: Workplace conversations, school morning greetings, medical consultations, and casual complaints among friends.

Nuance: It sounds slightly more conversational than 'suimin-busoku', which is the formal/technical equivalent.

最近、仕事が忙しくてずっと寝不足なんです。(Recently, I've been busy with work and have a constant lack of sleep.)

寝不足のせいで、集中力が続きません。(Because of lack of sleep, I can't maintain my concentration.)

彼はいつも寝不足そうな顔をしている。(He always looks like he's suffering from a lack of sleep.)

試験の前日は寝不足になりがちだ。(One tends to get insufficient sleep the day before an exam.)

ひどい寝不足で、目の下にクマができてしまった。(Due to severe lack of sleep, I got dark circles under my eyes.)

To truly master this word, one must understand that 'nebusoku' is often paired with the particle 'de' (で) to indicate a cause or reason. For example, 'Nebusoku de atama ga itai' (I have a headache due to lack of sleep). It can also be treated as a state using 'da' or 'desu'. Unlike English where we say 'I didn't sleep enough' (a verb phrase), Japanese speakers frequently use the noun 'nebusoku' to encapsulate the entire experience. This noun-centric approach is a hallmark of Japanese efficiency in communication. Furthermore, the term is deeply tied to the Japanese concept of 'Inemuri' (sleeping while present), where people might nap on trains or in meetings because of their chronic 'nebusoku'. Understanding this word provides a window into the daily struggles of the Japanese urban population.

Using 寝不足 (Nebusoku) correctly involves understanding its role as a noun and how it interacts with various Japanese particles. The most common pattern is [Noun] + [Particle]. Because 'nebusoku' describes a state or a cause, the particles 'de' (で), 'ga' (が), and 'no' (の) are frequently employed. When you want to say that something happened *because* of your lack of sleep, you use 'nebusoku de'. If you want to say you *have* a lack of sleep, you use 'nebusoku da' or 'nebusoku desu'. If you are describing a person who is sleep-deprived, you use 'nebusoku no [person]'.

Pattern: Cause and Effect: 寝不足で (Nebusoku de...) - Because of lack of sleep... (e.g., Nebusoku de akubi ga deru - I'm yawning because of lack of sleep).

Pattern: Description: 寝不足の (Nebusoku no...) - Sleep-deprived [Noun] (e.g., Nebusoku no unten-shu - A sleep-deprived driver).

Pattern: Identification: 寝不足だ (Nebusoku da) - It is a lack of sleep / I am sleep-deprived.

昨夜はゲームを遅くまでしていたので、今日はひどい寝不足だ。(I played games until late last night, so I'm severely sleep-deprived today.)

寝不足が続くと、免疫力が下がって風邪を引きやすくなります。(If lack of sleep continues, your immunity drops and you easily catch a cold.)

「顔色が悪いね」「うん、ちょっと寝不足なんだ」("You look pale." "Yeah, I'm a bit short on sleep.")

慢性的な寝不足は、精神的なストレスの原因にもなり得ます。(Chronic lack of sleep can also be a cause of mental stress.)

お肌の荒れは、寝不足が原因かもしれません。(Your skin irritation might be caused by a lack of sleep.)

Furthermore, 'nebusoku' is often used in the phrase 'nebusoku-gimi' (寝不足気味), which means 'feeling a bit short on sleep' or 'slightly sleep-deprived'. The suffix '-gimi' adds a layer of subjectivity and mildness to the statement. In a business context, if you need to apologize for a slight lack of focus, you might say, 'Kyou wa chotto nebusoku-gimi de...' (I'm feeling a bit short on sleep today, so...). This is a very natural way to soften the impact of your condition while still being honest. In written Japanese, particularly in health articles, you will see 'nebusoku' used as a subject to describe various health risks. It is a versatile word that bridges the gap between everyday casual speech and informative writing.

You will encounter 寝不足 (Nebusoku) in almost every corner of Japanese daily life. It is perhaps one of the most frequently used terms for physical self-assessment. In the morning, as coworkers gather at the office coffee machine, the word 'nebusoku' is as common as 'ohayou gozaimasu'. It serves as a social lubricant, allowing people to bond over their shared exhaustion in a high-pressure society. On television, particularly in morning variety shows (wide shows), health segments often focus on 'nebusoku' and its cures, featuring doctors who explain the science of sleep. You'll also hear it in anime and manga, where characters are often depicted with dark circles under their eyes after late-night study sessions or battles.

In the Office: Used to explain why someone might be yawning or less productive. 'Kinou wa zangyou de nebusoku desu' (I'm short on sleep because of overtime yesterday).

At School: Students use it after staying up late for exams or playing video games. 'Tesuto-benkyou de nebusoku da...' (I'm sleep-deprived from studying for the test).

Media & News: News reports on traffic accidents often cite 'nebusoku unten' (sleep-deprived driving) as a major cause.

「最近、ずっと寝不足なんだよね」「無理しないで、早く寝なよ」("I've been short on sleep lately." "Don't overdo it, go to bed early.")

テレビ番組：寝不足を解消する５つの方法。(TV Program: 5 ways to resolve lack of sleep.)

「あー、寝不足で頭が働かない！」("Ah, my brain isn't working because of lack of sleep!")

駅のポスター：寝不足での運転は大変危険です。(Station poster: Driving while sleep-deprived is very dangerous.)

SNSの投稿：昨日ドラマを一気見して寝不足。でも面白かった！(SNS post: Binge-watched a drama yesterday and now I'm sleep-deprived. But it was fun!)

Furthermore, in medical contexts, a doctor might ask, 'Nebusoku wa arimasen ka?' (Do you have any lack of sleep?). It's a standard screening question for everything from high blood pressure to mental health. In the beauty industry, 'nebusoku' is frequently cited as the enemy of 'bihada' (beautiful skin). You will see it on the packaging of eye creams and energy drinks. In essence, 'nebusoku' is a word that describes a national struggle, making it an essential term for anyone living in or studying Japanese culture. It reflects the tension between the desire for productivity and the biological need for rest.

While 寝不足 (Nebusoku) is a common word, English speakers often make specific errors when integrating it into their Japanese. The most frequent mistake is treating it like a verb or an i-adjective. Since 'sleepy' is 'nemui' (an i-adjective), learners often try to conjugate 'nebusoku' in a similar way, which is incorrect. Another common pitfall is the confusion between 'nebusoku' and its more formal cousin 'suimin-busoku'. While they mean the same thing, using the formal version in a casual conversation with friends can sound overly clinical or stiff.

Mistake: Verbalizing it: Incorrect: 'Nebusoku-shimasu' or 'Nebusoku-shita'. Correct: 'Nebusoku da' or 'Nebusoku ni natta'.

Mistake: Confusing with 'Nemui': 'Nemui' is the feeling (I feel sleepy). 'Nebusoku' is the cause (I didn't sleep enough). Don't say 'Nebusoku desu' when you just mean you want to take a nap right now.

Mistake: Particle Choice: Using 'nebusoku o' (treating it as a direct object) is rare. Usually, it's the subject (ga) or the cause (de).

Incorrect: 寝不足する (Nebusoku-suru) - This is grammatically wrong because 'nebusoku' is not a suru-verb.

Incorrect: 寝不足い (Nebusokui) - Adding 'i' to make it an adjective is a common error based on 'nemui'.

Correct: 寝不足になる (Nebusoku ni naru) - To become sleep-deprived.

Correct: 寝不足だ (Nebusoku da) - I am (in a state of) lack of sleep.

Nuance Check: 睡眠不足 (Suimin-busoku) is better for doctors; 寝不足 (Nebusoku) is better for friends.

Another error is using 'nebusoku' to describe a single instance of staying up late. While it can be used that way, 'tetsuya' (彻夜 - staying up all night) is more accurate for a complete lack of sleep over one night. 'Nebusoku' usually implies a deficit—sleeping 4 hours instead of 8. Additionally, avoid using 'nebusoku' with positive outcomes. You wouldn't say 'Nebusoku de ureshii' (I'm happy because of lack of sleep). It is almost exclusively used in negative or neutral contexts where the lack of sleep is a burden or a physiological fact. By paying attention to these nuances, you can avoid the common 'gaijin' (foreigner) mistakes and sound more like a native speaker.

To expand your Japanese vocabulary beyond 寝不足 (Nebusoku), it is helpful to look at related terms that describe different aspects of sleep or the lack thereof. Each word has a specific nuance that makes it suitable for different situations. For instance, while 'nebusoku' is general, 'suimin-busoku' is technical, and 'tetsuya' is extreme. Understanding these differences allows for more precise expression of your physical state.

睡眠不足 (Suimin-busoku): Comparison: This is the formal/academic version of 'nebusoku'. Use it in medical reports, news articles, or formal speeches. It sounds more professional.

徹夜 (Tetsuya): Comparison: This means 'all-nighter'. While 'nebusoku' means you slept a little, 'tetsuya' means you didn't sleep at all. It is often used as a suru-verb: 'Tetsuya-suru'.

夜更かし (Yokashashi): Comparison: This means 'staying up late'. It focuses on the act of being awake late at night, rather than the resulting tiredness the next day. It's often used for leisure activities.

睡眠不足は万病の元です。(Sleep deprivation is the source of all diseases - Formal/Medical style.)

昨日、レポートのために徹夜しました。(I stayed up all night yesterday for my report.)

週末はついつい夜更かししてしまいます。(I accidentally end up staying up late on weekends.)

眠りが浅い (Nemuri ga asai) - This means 'shallow sleep'. It describes the quality of sleep rather than the quantity.

熟睡 (Jukusui) - This is the opposite of nebusoku; it means 'deep/sound sleep'.

Finally, consider 'fumin' (不眠), which means 'insomnia'. While 'nebusoku' might be your own fault (like staying up to watch a movie), 'fumin' implies a medical inability to sleep despite wanting to. If you tell a doctor you have 'nebusoku', they might tell you to go to bed earlier. If you tell them you have 'fumin', they might prescribe medication. Understanding these distinctions is crucial for accurate communication. By mastering this cluster of words, you can describe your nocturnal habits and their daytime consequences with the same precision as a native Japanese speaker.

How Formal Is It?

Fun Fact

The kanji for 'busoku' (不足) literally means 'not enough feet'. In ancient Chinese, 'feet' was used to represent 'sufficiency' or 'walking to completion'.

Pronunciation Guide

UK /ne̞bu̥so̞ku͍/

US /neɪbuːsoʊkuː/

Heiban (Flat) pitch accent in most dialects, meaning the pitch stays relatively level after the first syllable.

Rhymes With

Koku (Nation) Zoku (Group) Moku (Eye) Roku (Six) Doku (Poison) Yoku (Greed) Hoku (North) Choku (Direct)

Common Errors

Pronouncing it as 'ne-bu-so-ku' with four equal beats (English style) instead of the Japanese mora timing.
Stressing the 'bu' too much.
Confusing the pitch accent with 'nemui'.
Mispronouncing 'soku' as 'zoku'.
Devoicing the wrong vowels.

Difficulty Rating

Reading 3/5

The kanji are common but require B1 level knowledge.

Writing 4/5

Writing '寝' (ne) can be tricky due to the number of strokes.

Speaking 2/5

Pronunciation is straightforward for English speakers.

Listening 2/5

Commonly used and easy to distinguish in speech.

What to Learn Next

Prerequisites

寝る (Neru) 不足 (Busoku) 眠い (Nemui) 昨日 (Kinou) 忙しい (Isogashii)

Learn Next

睡眠 (Suimin) 徹夜 (Tetsuya) 不眠 (Fumin) 熟睡 (Jukusui) 健康 (Kenkou)

Advanced

自律神経 (Jiritsu shinkei) 体内時計 (Tainai dokei) レム睡眠 (Remu suimin) ノンレム睡眠 (Non-remu suimin) 睡眠負債 (Suimin fusai)

Grammar to Know

Noun + で (Cause/Reason)

寝不足で頭が痛い。

Noun + になる (Become)

忙しくて寝不足になった。

Noun + 気味 (Tendency/Feeling)

今日は寝不足気味だ。

Noun + のせいで (Negative Cause)

寝不足のせいで遅刻した。

Noun + が続く (Continuation)

寝不足が続いている。

Examples by Level

今日は寝不足です。

I am short on sleep today.

Uses 'desu' to state a condition.

寝不足で眠いです。

I'm sleepy because of lack of sleep.

'de' marks the reason.

昨日は寝不足でした。

I was short on sleep yesterday.

Past tense of 'desu'.

寝不足は体に悪いです。

Lack of sleep is bad for the body.

'wa' marks the topic.

田中さんは寝不足ですか？

Is Mr. Tanaka short on sleep?

Question form.

ちょっと寝不足です。

I'm a little short on sleep.

'chotto' as an adverb.

寝不足は嫌いです。

I hate lack of sleep.

'kirai' expresses dislike.

毎日寝不足です。

I'm short on sleep every day.

'mainichi' shows frequency.

寝不足の時は、コーヒーを飲みます。

When I lack sleep, I drink coffee.

'toki' means 'when'.

寝不足にならないように、早く寝ます。

I go to bed early so I don't get sleep-deprived.

'ni naru' means 'to become'.

ひどい寝不足で、頭がいたいです。

I have a headache due to severe lack of sleep.

'hidoi' (severe) modifies the noun.

寝不足の顔をしていますね。

You have a sleep-deprived face.

'no' connects two nouns.

仕事が忙しくて、ずっと寝不足です。

I've been busy with work and constantly short on sleep.

'te-form' of 'isogashii' shows reason.

寝不足だと、勉強ができません。

If I lack sleep, I can't study.

'dato' acts as a conditional 'if'.

昨夜はゲームで寝不足になりました。

I became sleep-deprived because of games last night.

'de' marks the activity cause.

寝不足の日は、早く帰りたいです。

On days when I lack sleep, I want to go home early.

Modifying 'hi' (day).

最近、寝不足気味なので、今日は早く寝ます。

I'm feeling a bit short on sleep lately, so I'll go to bed early today.

'-gimi' means 'feeling like' or 'tending to'.

寝不足が続くと、仕事でミスをしやすくなります。

If lack of sleep continues, it becomes easy to make mistakes at work.

'-yasuku naru' means 'become easy to do'.

慢性的な寝不足は、健康に大きな影響を与えます。

Chronic lack of sleep has a big impact on health.

'mansei-teki' means 'chronic'.

寝不足のせいで、集中力が全くありません。

Because of lack of sleep, I have no concentration at all.

'no sei de' marks a negative cause.

彼は寝不足を解消するために、昼寝をしました。

He took a nap to resolve his lack of sleep.

'tame ni' shows purpose.

試験前は、どうしても寝不足になりがちです。

Before exams, one tends to get sleep-deprived no matter what.

'-gachi' means 'tends to'.

寝不足の状態では、車の運転は控えるべきです。

In a state of sleep deprivation, you should refrain from driving.

'-beki' means 'should'.

彼女は寝不足そうな顔で会議に出席した。

She attended the meeting with a face that looked sleep-deprived.

'-sou na' means 'looking like'.

日本の会社員は、慢性的な寝不足に悩まされていると言われている。

It is said that Japanese office workers suffer from chronic lack of sleep.

Passive voice 'nayamasareru' (to be troubled by).

寝不足が蓄積すると、感情のコントロールが難しくなることがある。

When lack of sleep accumulates, it can become difficult to control emotions.

'chikuseki suru' means 'to accumulate'.

今回の事故の主な原因は、運転手の寝不足によるものだった。

The main cause of this accident was due to the driver's lack of sleep.

'ni yoru mono' indicates a cause/source.

寝不足を自覚している人は多いが、改善するのは容易ではない。

Many people are aware of their lack of sleep, but improving it is not easy.

'jikaku suru' means 'to be self-aware'.

休日に寝溜めをしても、平日の寝不足は解消されない。

Even if you sleep in on weekends, the weekday sleep deprivation isn't resolved.

'nedame' means 'sleeping to make up for lost time'.

寝不足は判断力を鈍らせ、仕事の効率を著しく低下させる。

Lack of sleep dulls judgment and significantly lowers work efficiency.

'niburaseru' is the causative form of 'nibui' (dull).

過度な寝不足は、幻覚や妄想を引き起こす危険性がある。

Excessive lack of sleep carries the risk of causing hallucinations and delusions.

'hikio-okosu' means 'to cause/trigger'.

現代社会において、寝不足は深刻な社会問題の一つとなっている。

In modern society, lack of sleep has become one of the serious social issues.

'ni oite' means 'in' or 'regarding'.

睡眠の質が伴わない寝不足は、認知機能の低下に直結する。

Lack of sleep without quality results directly in a decline in cognitive function.

'tomonawanai' means 'not accompanied by'.

企業は従業員の寝不足がもたらす経済的損失を軽視すべきではない。

Companies should not underestimate the economic losses caused by employee sleep deprivation.

'motarasu' means 'to bring about/cause'.

寝不足が常態化している社会では、メンタルヘルスへの配慮が不可欠だ。

In a society where lack of sleep has become normalized, consideration for mental health is essential.

'joutai-ka' means 'normalization/becoming a habit'.

アスリートにとって、わずかな寝不足もパフォーマンスに致命的な影響を及ぼしかねない。

For athletes, even a slight lack of sleep could potentially have a fatal impact on performance.

'-kanenai' expresses a risk or possibility of a negative outcome.

寝不足による注意力の散漫が、取り返しのつかない大惨事を招くこともある。

Distraction due to lack of sleep can sometimes lead to an irreversible catastrophe.

'torikaeshi no tsukanai' means 'irreversible'.

育児中の親にとって、慢性的な寝不足は避けられない試練である。

For parents raising children, chronic lack of sleep is an unavoidable ordeal.

'shiren' means 'ordeal' or 'trial'.

寝不足の蓄積、いわゆる「睡眠負債」を返済するのは一筋縄ではいかない。

Repaying the accumulation of sleep deprivation, the so-called 'sleep debt', is no easy task.

'hitosujinawa dewa ikanai' is an idiom meaning 'not straightforward'.

長時間の残業が美徳とされる文化が、国民的な寝不足を助長している側面がある。

There is an aspect where the culture of long overtime being seen as a virtue encourages national sleep deprivation.

'jojo suru' means 'to promote/encourage (something bad)'.

寝不足が脳内のアミロイドβの蓄積を促し、アルツハイマー病のリスクを高めるという研究結果がある。

There are research results suggesting that lack of sleep promotes the accumulation of amyloid beta in the brain, increasing the risk of Alzheimer's disease.

Technical scientific sentence structure.

現代人の寝不足は、単なる個人の怠慢ではなく、構造的な社会の歪みが露呈したものと言えよう。

The sleep deprivation of modern people is not merely individual negligence, but rather an exposure of structural societal distortions.

'-to ieyou' is a formal way to say 'one might say'.

寝不足がもたらす情動の不安定さは、対人関係における摩擦の温床となり得る。

The emotional instability caused by lack of sleep can become a breeding ground for friction in interpersonal relationships.

'onshou' means 'breeding ground' or 'hotbed'.

睡眠文化の変遷を辿ると、産業革命以降、人類は恒常的な寝不足に陥ったことが分かる。

Tracing the transition of sleep culture reveals that since the Industrial Revolution, humanity has fallen into a state of constant sleep deprivation.

'koujou-teki' means 'constant/perpetual'.

寝不足による経済的損失は、GDPの数パーセントに及ぶという試算もなされている。

Calculations have been made suggesting that economic losses due to lack of sleep amount to several percent of GDP.

'shisan' means 'provisional calculation'.

「寝不足」という言葉の裏には、日本人の勤勉さと、それに伴う自己犠牲の精神が垣間見える。

Behind the word 'nebusoku', one can catch a glimpse of the diligence of the Japanese people and the accompanying spirit of self-sacrifice.

'kaimieru' means 'to catch a glimpse of'.

寝不足を美徳とする風潮を打破し、十分な休息を権利として確立することが急務である。

It is an urgent matter to break the trend of viewing lack of sleep as a virtue and to establish sufficient rest as a right.

'kyuumu' means 'urgent business/priority'.

寝不足が引き起こす微細な認知のズレが、やがて巨大なシステムの崩壊を招くリスクを孕んでいる。

The minute cognitive shifts caused by lack of sleep carry the risk of eventually leading to the collapse of giant systems.

'haramu' means 'to be fraught with' or 'to contain'.

Synonyms

睡眠不足 (Suimin-busoku) 徹夜 (Tetsuya) 夜更かし (Yokashashi) 不眠 (Fumin) 眠気 (Nemuke) 浅い眠り (Asai nemuri) 寝足りない (Netarinai) 睡眠欠乏 (Suimin-ketsubou)

Antonyms

熟睡 (Jukusui) 快眠 (Kaimin) 安眠 (Anmin) 寝過ぎ (Nesugi)

Common Collocations

寝不足が続く

寝不足を解消する

ひどい寝不足

寝不足で頭が痛い

寝不足のせい

慢性的な寝不足

寝不足気味

寝不足による事故

寝不足になる

寝不足の顔

Common Phrases

寝不足は万病の元

— Lack of sleep is the root of all illness. A common saying about health.

寝不足は万病の元だから、早く寝なさい。

寝不足のクマ

— Dark circles under the eyes caused by lack of sleep.

寝不足のクマがひどいね。

万年寝不足

— Always being sleep-deprived (perpetual lack of sleep).

私は万年寝不足です。

寝不足解消法

— Ways/methods to resolve a lack of sleep.

おすすめの寝不足解消法を教えて。

寝不足運転

— Driving while sleep-deprived (similar to drunk driving).

寝不足運転は絶対にダメだ。

寝不足自慢

— Bragging about how little sleep one got (common in Japan).

寝不足自慢はやめよう。

寝不足注意報

— A metaphorical 'warning' that one is getting too little sleep.

自分に寝不足注意報を出した。

寝不足マックス

— Slang for being at the maximum level of sleep deprivation.

今、寝不足マックスだよ。

寝不足ダウン

— Collapsing or becoming sick due to lack of sleep.

寝不足ダウンで会社を休んだ。

寝不足ストレス

— Stress caused by not getting enough sleep.

寝不足ストレスがたまっている。

Often Confused With

寝不足 vs 眠い (Nemui)

Nemui is the feeling of sleepiness; Nebusoku is the lack of sleep that causes it.

寝不足 vs 徹夜 (Tetsuya)

Tetsuya means no sleep at all; Nebusoku means some sleep, but not enough.

寝不足 vs 不眠 (Fumin)

Fumin is the medical condition of insomnia; Nebusoku is often situational.

Idioms & Expressions

"目をこする"

— To rub one's eyes. Often done when suffering from 'nebusoku'.

寝不足で目をこすりながら起きた。

Neutral

"船を漕ぐ"

— To nod off (literally 'to row a boat'). This happens when 'nebusoku' hits during a meeting.

会議中に船を漕いでしまった。

Idiomatic

"目がしょぼしょぼする"

— Eyes feeling bleary or tired from lack of sleep.

寝不足で目がしょぼしょぼする。

Casual

"頭がぼんやりする"

— One's head feels foggy or spaced out due to 'nebusoku'.

寝不足で頭がぼんやりする。

Neutral

"生あくびが出る"

— Frequent yawning that isn't deep, often due to fatigue or 'nebusoku'.

寝不足で生あくびが止まらない。

Neutral

"泥のように眠る"

— To sleep like a log (literally 'like mud') to recover from 'nebusoku'.

週末は泥のように眠った。

Idiomatic

"一睡もできない"

— Not being able to sleep a wink (extreme 'nebusoku').

昨夜は一睡もできなかった。

Neutral

"寝る間も惜しんで"

— Begrudging even the time to sleep (working extremely hard).

寝る間も惜しんで勉強した。

Idiomatic

"仮眠を取る"

— To take a short nap to mitigate 'nebusoku'.

デスクで仮眠を取った。

Neutral

"睡魔に襲われる"

— To be overcome by the 'sleep demon' (sudden intense sleepiness).

午後の授業で睡魔に襲われた。

Literary

Easily Confused

寝不足 vs 睡眠不足 (Suimin-busoku)

They mean the same thing.

Suimin-busoku is formal/academic; Nebusoku is casual/daily life. Use the former with doctors and the latter with friends.

医師は睡眠不足を警告した。 (The doctor warned about sleep deprivation.)

寝不足 vs 夜更かし (Yokashashi)

Both involve being awake late.

Yokashashi is the *act* of staying up late (often voluntary). Nebusoku is the *result* (lack of sleep).

夜更かしの結果、寝不足になった。 (As a result of staying up late, I became sleep-deprived.)

寝不足 vs 寝坊 (Nebou)

Both relate to sleep and problems.

Nebou is oversleeping (waking up late). Nebusoku is not sleeping enough (going to bed late or waking up too early).

寝不足だったので、寝坊してしまった。 (Because I was sleep-deprived, I ended up oversleeping.)

寝不足 vs 二度寝 (Nidone)

Relates to the morning sleep cycle.

Nidone is going back to sleep after waking up once. It's often a 'cure' for feeling nebusoku.

寝不足だったので、二度寝した。 (Since I was sleep-deprived, I went back to sleep.)

寝不足 vs 居眠り (Inemuri)

Both involve tiredness.

Inemuri is napping while present (at work/school). It is the *action* taken because one is nebusoku.

寝不足で居眠りをしてしまった。 (I dozed off because of lack of sleep.)

Sentence Patterns

[Subject] は寝不足です。

私は寝不足です。

寝不足で [State] です。

寝不足で眠いです。

寝不足気味なので、[Action]。

寝不足気味なので、早く寝ます。

寝不足のせいで [Negative Result]。

寝不足のせいでミスをした。

寝不足が続くと [Consequence]。

寝不足が続くと病気になる。

[Activity] による寝不足。

仕事による寝不足。

寝不足を解消するために [Method]。

寝不足を解消するために昼寝する。

寝不足が常態化している。

現代社会は寝不足が常態化している。

Word Family

Nouns

睡眠 (Suimin) - Sleep

不足 (Busoku) - Lack

寝顔 (Negao) - Sleeping face

寝坊 (Nebou) - Oversleeping

Verbs

寝る (Neru) - To sleep

寝かす (Nekasu) - To put to sleep

寝そべる (Nesoberu) - To sprawl out

Adjectives

眠い (Nemui) - Sleepy

眠たい (Nemutai) - Sleepy (casual/regional)

寝苦しい (Negurushii) - Hard to sleep

布団 (Futon)

枕 (Makura) - Pillow

夢 (Yume) - Dream

目覚まし時計 (Mezamashi-dokei) - Alarm clock

羊 (Hitsuji) - Sheep

How to Use It

frequency

Extremely high in daily life, especially in urban areas.

Common Mistakes

Using 'nebusoku' as a verb (e.g., nebusoku-shimasu). → Nebusoku desu / Nebusoku ni naru.
'Nebusoku' is a noun, not a suru-verb. You must use a copula or a verb like 'naru'.
Saying 'nebusoku' when you just feel sleepy right now. → Nemui desu.
'Nebusoku' is the chronic state or the cause. 'Nemui' is the immediate feeling. Use 'nemui' for the feeling.
Treating 'nebusoku' as an i-adjective (e.g., nebusokui). → Nebusoku na / Nebusoku no.
Learners often mix it up with 'nemui'. It is a noun, so it needs 'no' or 'na' (in some cases) to modify.
Confusing 'nebusoku' with 'nebou' (oversleeping). → Nebou (for waking up late); Nebusoku (for not sleeping enough).
These are opposites in a way. One is too much/late sleep, the other is too little sleep.
Using 'nebusoku' for a medical condition in a formal report. → Suimin-busoku.
'Nebusoku' is too casual for academic or very formal writing. Use 'suimin-busoku' instead.

Tips

Use 'de' for Cause

Always use 'nebusoku de' when you want to link it to a symptom like a headache or a mistake. It's the most natural way to show cause and effect.

Learn the Antonym

Learn '熟睡' (jukusui - deep sleep) along with 'nebusoku'. Being able to say you finally got deep sleep after being sleep-deprived makes your Japanese sound more balanced.

The 'Badge of Honor'

Understand that in Japan, saying you're 'nebusoku' can sometimes be a way of showing off how busy and important you are. This is called 'isogashii-jiman' (busy-bragging).

Watch the 'u'

In the 'bu' and 'ku' parts of 'nebusoku', the 'u' sound is very short or even silent. Don't over-pronounce 'boo-soo-koo'.

Kanji Practice

The kanji '寝' is quite complex. Practice the 'crown' radical at the top and the 'miki' (trunk) part in the middle to get the balance right.

Nebusoku vs. Tetsuya

If you stayed up until 4 AM and woke up at 7 AM, you are 'nebusoku'. If you didn't sleep at all, you are 'tetsuya'. Choose the right one for accuracy.

Morning Greeting

If a Japanese coworker looks tired, asking 'Nebusoku desu ka?' is a very common and empathetic way to start a conversation in the morning.

Use Suimin-busoku with Doctors

If you go to a clinic in Japan, use 'suimin-busoku'. It sounds more precise and helps the doctor understand you are talking about a physical condition.

The power of -gimi

Adding '-gimi' makes you sound more like a native. It's perfect for when you're just starting to feel the effects of a few late nights.

Don't say 'Nebusoku-shita'

Remember, it's a noun. Use 'nebusoku ni natta' (became sleep-deprived) instead of trying to make it a verb.

Memorize It

Mnemonic

Think of 'NE' as 'Night Energy' and 'BUSOKU' as 'Broken Supply'. If your Night Energy Supply is Broken, you have NE-BUSOKU.

Visual Association

Imagine a person standing on one 'foot' (soku) because they are missing the other—they are 'insufficient' (busoku) and falling asleep (ne).

Word Web

Sleep Tired Coffee Overtime Exams Headache Yawn Night

Challenge

Try to use 'nebusoku' in a sentence today when someone asks how you are. Instead of 'genki desu', try 'chotto nebusoku desu'.

Word Origin

Formed by the combination of the kun-reading 'ne' (from the verb 'neru') and the on-reading 'busoku' (from Middle Chinese roots). It reflects a hybrid of native Japanese and borrowed Sinitic vocabulary.

Original meaning: Literally 'sleep insufficiency'.

Japonic (Ne) + Sino-Japanese (Busoku).

Cultural Context

Be careful not to sound like you are bragging about 'nebusoku' too much, as modern Japanese people are becoming more health-conscious.

In English, we usually use verb phrases like 'I didn't sleep enough' rather than the noun 'lack of sleep' in casual talk.

The 'Sleep Debt' (睡眠負債) trend in Japanese media. Anime tropes of characters with dark circles (e.g., L from Death Note). Salaryman 'Inemuri' photos on social media.

Practice in Real Life

Real-World Contexts

At the Office

寝不足でミスをしました。
昨日は残業で寝不足です。
コーヒーでも飲んで寝不足を解消しましょう。
寝不足気味なので、お先に失礼します。

At School

テスト勉強で寝不足だ。
寝不足で授業中に寝てしまった。
みんな寝不足そうな顔をしてるね。
寝不足は成績に響くよ。

At the Doctor

最近、寝不足が続いています。
寝不足のせいか、頭痛がします。
寝不足を治す方法はありますか？
慢性的な寝不足です。

With Friends

昨日飲みすぎて寝不足だよ。
寝不足のクマがすごいことになってる！
今日は寝不足だから早く帰るね。
寝不足マックスで死にそう。

On Social Media

#寝不足
夜更かしして寝不足なう。
寝不足だけど仕事頑張る。
寝不足解消したい。

Conversation Starters

"「最近、寝不足じゃないですか？」 (Haven't you been short on sleep lately?)"

"「寝不足の時、どうやってリフレッシュしていますか？」 (How do you refresh when you're sleep-deprived?)"

"「昨日は何時間寝ましたか？私は寝不足です。」 (How many hours did you sleep yesterday? I'm short on sleep.)"

"「寝不足で頭が働かないことってありますよね。」 (There are times when your brain doesn't work due to lack of sleep, right?)"

"「おすすめの寝不足解消グッズはありますか？」 (Do you have any recommended goods for resolving lack of sleep?)"

Journal Prompts

今日は寝不足ですか？その理由を詳しく書いてください。 (Are you sleep-deprived today? Write the reason in detail.)

寝不足の時、あなたの体や心にはどんな変化がありますか？ (When you are sleep-deprived, what changes occur in your body and mind?)

日本の「寝不足文化」について、どう思いますか？ (What do you think about Japan's 'nebusoku culture'?)

最高の睡眠をとるために、今夜は何をしますか？ (What will you do tonight to get the best sleep?)

寝不足で失敗した経験があれば、書いてください。 (If you have an experience of failing due to lack of sleep, please write it.)

Frequently Asked Questions

10 questions

No, 'nebusoku' is a noun. You cannot say 'nebusoku-suru'. To express the action, use 'nebusoku ni naru' (to become sleep-deprived) or simply state the condition with 'nebusoku da'.

The primary difference is formality. 'Nebusoku' is used in everyday conversation with friends and family. 'Suimin-busoku' is more clinical and formal, used in news, medical reports, and professional settings.

Not exactly. 'Nebusoku' describes the *reason* you are sleepy. If you want to say 'I'm sleepy,' use 'nemui'. Use 'nebusoku' if you want to explain that you didn't sleep enough last night.

You use the particle 'no'. For example, 'nebusoku no gakusei' (a sleep-deprived student) or 'nebusoku no hi' (a day of insufficient sleep).

Yes, it almost always implies a negative state or a problem. However, in some contexts, it can be used to show how hard you've been working, which might be seen as a positive trait by some.

The suffix '-gimi' (気味) means 'a touch of' or 'feeling a bit'. 'Nebusoku-gimi' means you feel like you haven't been getting quite enough sleep lately, but it's not extreme.

Usually, 'nebusoku' refers to the *amount* (quantity) of sleep. For quality, people say 'nemuri ga asai' (shallow sleep) or 'suimin no shitsu ga warui' (bad sleep quality).

The most common phrase is 'nebusoku o kaishou suru' (寝不足を解消する). You can also say 'nebusoku o oginau' (to make up for lack of sleep).

It depends on the relationship. In a casual office, it's fine as small talk. In a formal setting, it might sound like you are making excuses for poor performance, so use it carefully.

The kanji are 寝 (sleep), 不 (not), and 足 (enough/foot). Together they mean 'sleep not enough'.