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B2 adjective 10 min de lecture

不可欠な

fukaketsu na

Entraîne-toi Exemples Notes et astuces 不可欠な en 30 secondes

Explication 不可欠な in your Level:

At the A1 level, you usually learn basic words like 'hitsuyo' (necessary). 'Fukaketsu na' is a much more advanced word. Think of it as 'Super Necessary.' Imagine you are building a house. You 'need' (hitsuyo) paint, but you 'cannot do without' (fukaketsu) a roof. If the roof is missing, it's not a house! For A1 students, just remember that this word describes things you absolutely must have to survive or to finish a job. It's like saying 'must have' instead of 'want.' You might see it in very simple signs about safety or health, like 'Water is fukaketsu for life.' Even though it's a 'big' word, the idea is simple: 'No this, no success.' Don't worry about using it in your own speaking yet, but try to recognize the 'fu-ka-ketsu' kanji when you see them together.

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At the A2 level, you are starting to describe things in more detail. 'Fukaketsu na' is a na-adjective you can use to show that something is very important. In A2, you might use it to talk about your hobbies or studies. For example, 'To learn Japanese, a dictionary is fukaketsu' (日本語を勉強するのに、辞書は不可欠です). It sounds much stronger than just saying 'hitsuyo.' You should notice that it often comes before a noun with 'na' (不可欠なもの - an indispensable thing) or at the end of a sentence with 'desu' (不可欠です). It is a good word to learn if you want to emphasize that something is a 'key' part of your life. Just remember not to use it for small things like 'I need a cookie,' because it sounds too serious for that!

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At the B1 level, you are expected to understand more formal and abstract concepts. 'Fukaketsu na' becomes very useful here because it allows you to discuss logical requirements. You will see it in news articles and textbooks. Instead of just saying 'I need this,' you are now saying 'This element is indispensable for this result.' For example, when discussing the environment, you might say 'Renewable energy is fukaketsu for the future.' This word helps you connect ideas logically. You should also learn the common phrase '必要不可欠' (hitsuyo-fukaketsu), which is often used in writing to mean 'absolutely essential.' At this level, you should start trying to use 'fukaketsu' in your written essays to sound more professional and precise.

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At the B2 level, '不可欠な' is a core vocabulary item for academic and professional Japanese. You should be able to use it fluently to describe complex dependencies. For instance, in a business presentation, you might explain why a specific marketing strategy is 'fukaketsu' for reaching a new demographic. You should also understand the subtle difference between 'fukaketsu' and 'hissu' (mandatory). B2 learners should be comfortable using the pattern '〜にとって不可欠な' (indispensable for...). You are also expected to recognize it in various registers, from scientific papers discussing 'essential nutrients' to political discourse about 'indispensable rights.' This word is a key marker of a 'higher-intermediate' vocabulary, showing that you can distinguish between levels of necessity.

At the C1 level, you should have a nuanced command of '不可欠な' and its synonyms. You can use it to build persuasive arguments, emphasizing the logical necessity of your points. You will encounter it in complex literature and high-level philosophical or legal texts. At this level, you should also be aware of its role in compound technical terms and how it functions in formal 'da/de aru' style writing. You can distinguish between 'fukaketsu' (logical necessity), 'kakasenai' (natural/personal necessity), and 'kan'yo' (vital importance). C1 learners should be able to use 'fukaketsu' to describe abstract concepts like 'trust is indispensable for social cohesion' or 'innovation is indispensable for economic survival' with perfect grammatical accuracy and appropriate register.

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At the C2 level, '不可欠な' is a word you use with complete native-like precision. You understand its historical weight and its place within the broader spectrum of Japanese adjectives of necessity. You can use it in highly specialized fields, such as theoretical physics or constitutional law, where the 'indispensability' of a variable or a right must be argued with absolute clarity. You also recognize when the word is being used rhetorically to create a sense of urgency or gravity. A C2 speaker can effortlessly switch between 'fukaketsu' and other high-level synonyms like 'kyuyo' (urgent necessity) or 'kan'yo' depending on the specific nuance required by the context. You are also capable of identifying if the word is being used in a tautological or redundant way in others' writing and can correct it for maximum impact.

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Entraîne-toi Exemples Notes et astuces

不可欠な en 30 secondes

Fukaketsu na means indispensable or absolutely necessary. It is a formal na-adjective used for critical requirements.
It is stronger than 'hitsuyo' (necessary) and implies that without it, the whole system or goal will fail.
Commonly used in business, science, and formal writing to describe essential nutrients, skills, or conditions.
Grammatically, it often appears as '不可欠な [Noun]' or '〜は不可欠だ' and is frequently paired with 'ni totte'.

The Japanese word 不可欠な (fukaketsu na) is a sophisticated na-adjective that translates to 'indispensable,' 'essential,' or 'absolutely necessary.' While the word 'hitsuyo' (必要) covers the general concept of 'need,' fukaketsu carries a much heavier weight. It suggests that if the element in question were missing, the entire structure, process, or life form would cease to function or exist. It is the linguistic equivalent of saying something is a 'sine qua non'—an essential condition without which something else is not possible.

Core Nuance: The nuance is absolute. It is not just about being helpful or important; it is about being an integral part of a whole. For example, while a car might need a radio to be comfortable, it needs an engine as a fukaketsu component.

現代社会において、インターネットは不可欠なインフラとなっている。(In modern society, the internet has become an indispensable infrastructure.)

This word is frequently used in formal writing, academic papers, news reports, and professional business settings. You will hear it when discussing critical success factors, biological requirements, or fundamental human rights. In everyday conversation, it is used when the speaker wants to emphasize that something is not negotiable or optional. It elevates the conversation from a simple 'I need this' to 'This is a fundamental requirement for my existence or success.'

Kanji Breakdown: The word is composed of three kanji: 不 (fu - non/not), 可 (ka - possible/can), and 欠 (ketsu - lack/missing). Literally, it means 'not possible to lack' or 'cannot be missing.' This etymological root helps learners remember that it refers to something that simply cannot be omitted.

成功するためには、忍耐強さが不可欠だ。(Perseverance is indispensable for success.)

In terms of register, while it is formal, it is not archaic. It is a 'living' academic word. You will find it in scientific journals describing 'essential amino acids' (不可欠アミノ酸) and in political speeches discussing 'essential security measures.' Because it is a na-adjective, it is very versatile; it can modify nouns directly (不可欠な役割 - indispensable role) or act as a predicate (〜は不可欠だ - ...is indispensable).

Usage Contexts: Commonly used in business strategy (不可欠な戦略), biological science (不可欠な栄養素), and social commentary (不可欠な権利). It emphasizes a logical or biological necessity that transcends mere desire.

チームの和を保つためには、互いの信頼が不可欠な要素です。(Mutual trust is an indispensable element for maintaining team harmony.)

Using 不可欠な (fukaketsu na) correctly requires an understanding of its grammatical function as a na-adjective. Most commonly, it precedes a noun to define it as an absolute requirement. This structure follows the pattern: [Noun A] + は + [Noun B] + にとって + 不可欠な + [Noun C] + だ. For example, 'Oxygen is an indispensable element for humans' would be '酸素は人間にとって不可欠な要素だ.'

Predicate Form: When used at the end of a sentence, the 'na' is dropped and replaced with 'da' or 'desu'. Example: '睡眠は健康に不可欠です' (Sleep is indispensable for health). This is the most direct way to state necessity.

このプロジェクトを完遂するには、あなたの協力が不可欠だ。(Your cooperation is indispensable to complete this project.)

One interesting aspect of fukaketsu is its ability to combine with other words to form compound nouns. You will often see '必要不可欠' (hitsuyo-fukaketsu), which combines 'necessary' and 'indispensable' for ultimate emphasis. This tautological phrasing is very common in Japanese business writing to express that something is absolutely, 100% required without any room for debate.

Adverbial Use: While rare, it can be used adverbially as '不可欠に' to modify a verb, though this is often replaced by phrases like '欠かせない' (kakasenai). However, sticking to the adjective form is safer and more common for learners.

良質な睡眠は、脳の機能を維持するために不可欠なプロセスです。(Quality sleep is an indispensable process for maintaining brain function.)

Another common pattern is [Condition] + には + [Noun] + が不可欠だ. This is used to set a condition for success or a specific outcome. For instance, 'To win the game (試合に勝つには), practice (練習) is indispensable (が不可欠だ).' This logical structure is very useful in argumentative essays or professional presentations where you are outlining requirements for a goal.

Formal Writing: In essays, it is often used to introduce a thesis or a main point. '...において、以下の要素が不可欠である' (...in this regard, the following elements are indispensable). This provides a clear, authoritative tone to the writing.

民主主義の存続には、言論の自由が不可欠な条件である。(Freedom of speech is an indispensable condition for the survival of democracy.)

You will encounter 不可欠な (fukaketsu na) across a variety of domains, from the high-stakes environment of a boardroom to the precise language of a medical laboratory. In the business world, executives use it to describe core competencies or strategic assets. If a company is discussing a merger, they might say that a specific technology is 'fukaketsu' to their future growth. It signals that the item is a non-negotiable part of the deal.

Science and Medicine: In biology, '不可欠アミノ酸' (fukaketsu amino-san) refers to essential amino acids that the body cannot synthesize on its own and must be obtained through diet. Here, the word takes on a literal, biological meaning: without these, life cannot be sustained. You will see this on health supplement labels and in nutritional science textbooks.

ビタミンCは、健康を維持するために不可欠な栄養素です。(Vitamin C is an indispensable nutrient for maintaining health.)

In news and media, journalists use fukaketsu to describe critical infrastructure or social requirements. During a natural disaster, news reports might state that 'clean water and electricity are fukaketsu for the recovery efforts.' It adds a sense of urgency and gravity to the situation that the word 'hitsuyo' might lack. It emphasizes that these are not just 'needs' but 'survival requirements.'

Technology and Engineering: Software developers and engineers use this word when discussing system requirements. A specific library or a stable internet connection might be described as 'fukaketsu' for the application to run. It implies a technical dependency that cannot be bypassed.

このアプリの動作には、安定したネット環境が不可欠です。(A stable internet environment is indispensable for the operation of this app.)

Finally, in legal and political contexts, the term is used to define rights or conditions. Constitutional law might describe certain freedoms as 'fukaketsu' to a democratic society. In international relations, diplomatic communication often highlights 'fukaketsu' conditions for peace treaties or trade agreements. In these cases, the word carries the weight of law and formal commitment.

Art and Creativity: Even in creative fields, a director might say that a certain actor's presence is 'fukaketsu' for the film's success. This highlights the unique, irreplaceable value of that person or element.

彼の独特な声は、この物語に不可欠な要素だ。(His unique voice is an indispensable element of this story.)

While 不可欠な (fukaketsu na) is a powerful word, its misuse can lead to unnatural Japanese or logical inconsistencies. The most common mistake is overuse in casual settings. Using fukaketsu when you just mean you 'really want' a coffee or 'need' to go to the store sounds overly dramatic, almost like a character in a historical play. For everyday needs, 'hitsuyo' (必要) or 'iru' (要る) is much more appropriate.

Confusion with 'Hitsuyo': Learners often treat 'hitsuyo' and 'fukaketsu' as interchangeable synonyms. However, 'hitsuyo' is a broad term for 'necessary,' while 'fukaketsu' specifically means 'indispensable.' If you say something is 'fukaketsu,' you are saying the goal is impossible without it. If it is just 'hitsuyo,' it is required, but perhaps there are alternatives.

❌ Incorrect: 明日のパーティーに、お菓子は不可欠だ。(Snacks are indispensable for tomorrow's party - sounds too dramatic).
✅ Correct: 明日のパーティーに、お菓子は必要だ。

Another mistake involves particle usage. Many students struggle with whether to use 'に' (ni) or 'にとって' (ni totte). While both can be correct, 'にとって' is generally used when something is indispensable from the perspective of a person or entity (e.g., 'To me, you are indispensable'). 'に' is often used for functional or logical necessity (e.g., 'Indispensable for health'). Using 'を' (wo) with fukaketsu is a common error as it is an adjective, not a verb.

Logical Redundancy: Avoid using '絶対' (zettai - absolutely) with '不可欠,' because 'fukaketsu' already implies 'absolute.' While '必要不可欠' is a standard set phrase, '絶対に不可欠' can sound a bit repetitive and cluttered in formal writing.

❌ Redundant: 水は生命に絶対に不可欠です。
✅ Natural: 水は生命に不可欠です。

Finally, learners sometimes confuse fukaketsu with hissu (必須). While similar, hissu is often used for administrative requirements (like a 'mandatory' field in a form), whereas fukaketsu is used for organic or logical requirements. If you are describing a required course at a university, use hissu. If you are describing the passion needed to graduate, use fukaketsu.

Summary of Misuse: 1. Using in trivial/casual contexts. 2. Forgetting the 'na' before nouns. 3. Using 'wo' as if it were a verb. 4. Over-modifying with 'zettai'.

学問の探求には、批判的な精神が不可欠な要素だ。(A critical spirit is an indispensable element in the pursuit of scholarship.)

Understanding the synonyms of 不可欠な (fukaketsu na) allows you to choose the exact shade of 'necessity' you wish to convey. While fukaketsu is the standard for 'indispensable,' other words offer slightly different registers or focuses.

1. 必須 (Hissu): Hissu is often translated as 'mandatory' or 'required.' It is very common in bureaucratic and educational contexts. A 'hissu kamoku' is a required subject you must take to graduate. It implies an external rule or requirement rather than an inherent logical necessity.

2. 必要 (Hitsuyo): Hitsuyo is the most general word for 'necessary.' It can be used for anything from 'I need a pen' to 'Oxygen is necessary for life.' It lacks the strong emphasis of 'indispensability' that fukaketsu provides.

比較:
1. 練習は必要だ (Practice is necessary).
2. 練習は不可欠だ (Practice is indispensable/vital).

For a more idiomatic or native-sounding alternative, you can use the verb phrase 欠かせない (kakasenai). This is the potential negative form of the verb 'kaku' (to lack/miss), meaning 'cannot be lacked.' It is slightly less formal than fukaketsu and is very common in both speech and writing. For example, 'Kore wa watashi ni totte kakasenai mono da' (This is something I cannot do without).

3. 肝心 (Kanjin): Kanjin means 'essential' or 'crucial' but often refers to a 'key point' or 'turning point.' It is used when identifying the most important part of a problem or a plan. 'Kanjin na no wa...' (The crucial thing is...).

4. 肝要 (Kan'yo): Kan'yo is a very formal, somewhat old-fashioned word meaning 'vital' or 'of great importance.' You might see this in older literature or very formal speeches by high-ranking officials.

健康を維持するには、バランスの取れた食事が欠かせない。(A balanced diet is indispensable for maintaining health.)

Finally, in very technical or philosophical discussions, you might encounter 固有の (koyu no), which means 'inherent' or 'intrinsic.' While not a direct synonym for 'indispensable,' it is often used when discussing properties that are essential to a thing's nature. Choosing between these words depends entirely on whether you are talking about a rule (hissu), a general need (hitsuyo), a logical requirement (fukaketsu), or a personal must-have (kakasenai).

How Formal Is It?

Le savais-tu ?

The kanji '欠' (ketsu) originally depicted a person with an open mouth, perhaps yawning or lacking something. Combined with 'fu' (not) and 'ka' (can), it creates a logical 'triple negative' feel of necessity.

Guide de prononciation

UK ɸɯᵝkaket͡sɯᵝna

US fukaketsuna

Japanese is a pitch-accent language. In 'fukaketsu', the pitch starts low on 'fu', rises on 'ka', and stays high through 'ketsu', then drops on 'na'.

Rime avec

Setsuna (刹那) Ketsuna (as in 潔な - rare) Setsuna (切な - stem of setsunai) Betsuna (別な) Tetsuna (as in 鉄な - colloquial) Metsuna (滅な) Zetsuna (絶な) Ketsuna (結な)

Erreurs fréquentes

Pronouncing 'fu' with the teeth on the lower lip like English 'f'.
Elongating the 'e' in 'ketsu' (it should be short).
Forgetting the 'na' when modifying a noun.
Putting too much stress on the 'tsu' syllable.
Misreading the kanji '欠' as '次'.

Niveau de difficulté

Lecture 4/5

The kanji are common but require N2 level knowledge to read fluently in context.

Écriture 4/5

Writing the kanji '欠' and '可' correctly takes practice, and the 'na' adjective usage must be precise.

Expression orale 3/5

The pronunciation is straightforward, but choosing the right register is the main challenge.

Écoute 3/5

Recognizable in formal news or business contexts, but may be missed if not familiar with 'fu-' prefixes.

Quoi apprendre ensuite

Prérequis

必要 (Hitsuyo) 欠ける (Kakeru) 可能 (Kanou) 重要 (Juyo) 存在 (Sonzai)

Apprends ensuite

必須 (Hissu) 肝要 (Kan'yo) 欠かせない (Kakasenai) 前提 (Zentei) 要素 (Yoso)

Avancé

枢要 (Suyo) 緊要 (Kinyo) 必至 (Hisshi) 絶対的 (Zettai-teki) 固有 (Koyu)

Grammaire à connaître

Na-Adjective noun modification (na)

不可欠な要素 (An indispensable element)

Predicate form with Da/Desu

水は不可欠だ (Water is indispensable)

Compound Noun formation

必要不可欠 (Absolutely essential)

Particle 'ni totte' for perspective

私にとって不可欠な存在 (An existence indispensable to me)

Particle 'ni' for purpose/target

健康に不可欠な運動 (Exercise indispensable for health)

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Exemples par niveau

水は体に不可欠です。

Water is indispensable for the body.

Simple predicate use: [Subject] wa [Noun] ni fukaketsu desu.

空気は生命に不可欠です。

Air is indispensable for life.

Using 'ni' to show what it is indispensable for.

勉強に本は不可欠だ。

Books are indispensable for study.

Informal ending 'da'.

野菜は健康に不可欠な食べ物だ。

Vegetables are indispensable food for health.

Modifying the noun 'tabemono' with 'na'.

睡眠は不可欠です。

Sleep is indispensable.

Short statement of necessity.

太陽は植物に不可欠だ。

The sun is indispensable for plants.

Simple A is indispensable for B structure.

愛は家族に不可欠なものだ。

Love is an indispensable thing for a family.

Using 'mono' (thing) at the end.

塩は料理に不可欠です。

Salt is indispensable for cooking.

Common everyday example.

日本語の勉強には辞書が不可欠です。

A dictionary is indispensable for studying Japanese.

Using 'ni wa' to emphasize the condition.

旅行にはパスポートが不可欠だ。

A passport is indispensable for travel.

Logical requirement for travel.

スマートフォンは今の生活に不可欠な道具だ。

Smartphones are indispensable tools for modern life.

Modifying 'dogu' (tool).

スポーツには練習が不可欠です。

Practice is indispensable for sports.

Standard A2 level necessity.

おいしい料理には新鮮な材料が不可欠だ。

Fresh ingredients are indispensable for delicious food.

Focus on quality requirement.

安全な運転には集中力が不可欠です。

Concentration is indispensable for safe driving.

Abstract noun 'shuchuryoku' as subject.

成功には努力が不可欠な要素だ。

Effort is an indispensable element for success.

Introducing 'yoso' (element).

友達は人生に不可欠な存在です。

Friends are an indispensable presence in life.

Using 'sonzai' (existence/presence).

現代社会において、インターネットは不可欠なインフラだ。

In modern society, the internet is an indispensable infrastructure.

Using 'ni oite' (in/at).

プロジェクトの成功にはチームワークが不可欠です。

Teamwork is indispensable for the success of the project.

Standard B1 business/academic phrase.

健康を維持するためには、適度な運動が不可欠だ。

To maintain health, moderate exercise is indispensable.

Using 'tame ni wa' (in order to).

彼のアドバイスは、私の決断にとって不可欠だった。

His advice was indispensable for my decision.

Past tense 'datta'.

この機械を動かすには専門的な知識が不可欠です。

Specialized knowledge is indispensable to operate this machine.

Using 'senmon-teki' (specialized).

信頼関係を築くには、正直さが不可欠な条件だ。

Honesty is an indispensable condition for building a relationship of trust.

Using 'joken' (condition).

経済の発展には、イノベーションが不可欠だと言われている。

It is said that innovation is indispensable for economic development.

Using 'to iwarete iru' (it is said that).

ビタミンは人間にとって不可欠な栄養素です。

Vitamins are indispensable nutrients for humans.

Using 'ni totte' (for/to).

グローバル化が進む中で、英語力は不可欠なスキルとなっている。

As globalization progresses, English proficiency is becoming an indispensable skill.

Using 'naka de' (amidst).

持続可能な発展のためには、環境保護が不可欠な課題だ。

Environmental protection is an indispensable issue for sustainable development.

Using 'kadai' (issue/task).

適切なリスク管理は、企業の存続に不可欠です。

Appropriate risk management is indispensable for a company's survival.

Using 'sonzoku' (survival/continuation).

民主主義を維持するためには、言論の自由が不可欠な要素である。

Freedom of speech is an indispensable element for maintaining democracy.

Formal 'de aru' ending.

この薬の成分は、治療プロセスにおいて不可欠な役割を果たす。

The components of this medicine play an indispensable role in the treatment process.

Using 'yakuwari o hatasu' (play a role).

質の高い教育は、国家の未来にとって不可欠な投資だ。

High-quality education is an indispensable investment for the nation's future.

Using 'toushi' (investment).

海外市場への進出には、現地の文化理解が不可欠だ。

Understanding the local culture is indispensable for expanding into overseas markets.

Using 'shinshutsu' (expansion/advance).

正確なデータ分析は、科学的な研究に不可欠なプロセスである。

Accurate data analysis is an indispensable process for scientific research.

Using 'bunseki' (analysis).

法的正義を実現するためには、適正な手続きが不可欠な要件とされる。

Proper procedures are considered an indispensable requirement for realizing legal justice.

Using 'yoken' (requirement) and passive 'sareru'.

自己実現の過程において、他者との対話は不可欠な契機となる。

In the process of self-actualization, dialogue with others becomes an indispensable catalyst.

Using 'keiki' (catalyst/opportunity).

複雑な社会問題を解決するには、多角的な視点が不可欠である。

To solve complex social problems, a multifaceted perspective is indispensable.

Using 'takaku-teki' (multifaceted).

平和の構築には、過去の歴史に対する真摯な反省が不可欠だ。

Sincere reflection on past history is indispensable for the construction of peace.

Using 'shinshi na' (sincere).

芸術的創造において、孤独は不可欠なスパイスのようなものだ。

In artistic creation, solitude is like an indispensable spice.

Metaphorical use.

企業の競争力を維持するためには、絶え間ない技術革新が不可欠である。

Constant technological innovation is indispensable for maintaining corporate competitiveness.

Using 'taemanai' (constant).

社会の安定には、公正な富の再分配が不可欠な要素として挙げられる。

Fair redistribution of wealth is cited as an indispensable element for social stability.

Using 'toshite agerareru' (is cited as).

真理の追究には、既存の価値観を疑う姿勢が不可欠だ。

An attitude of questioning existing values is indispensable for the pursuit of truth.

Using 'shisei' (attitude).

認識論的観点からすれば、主観と客観の峻別は不可欠な前提条件である。

From an epistemological point of view, the sharp distinction between subjective and objective is an indispensable prerequisite.

Highly academic terminology.

文明の存続可能性を模索する上で、資源の有限性を直視することは不可欠だ。

In exploring the sustainability of civilization, it is indispensable to face the finitude of resources.

Using 'mosaku suru' (exploring/groping for).

この哲学的命題を論じる際、言語の多義性への配慮は不可欠な要素となる。

When discussing this philosophical proposition, consideration of the ambiguity of language becomes an indispensable element.

Using 'tagisei' (ambiguity/polysemy).

高度に複雑化したシステムにおいては、冗長性の確保が不可欠な生存戦略である。

In highly complex systems, ensuring redundancy is an indispensable survival strategy.

Using 'jochousei' (redundancy).

文化の多様性を守ることは、人類の精神的豊かさを保つために不可欠な要諦だ。

Protecting cultural diversity is an indispensable vital point for maintaining the spiritual richness of humanity.

Using 'yotei' (vital point/secret).

政治的正当性を担保するには、民意の反映が不可欠なメカニズムとして機能しなければならない。

To guarantee political legitimacy, the reflection of the public will must function as an indispensable mechanism.

Using 'tanpo suru' (guarantee/secure).

科学の進歩には、パラダイムシフトを許容する柔軟な思考が不可欠な土壌となる。

For the progress of science, flexible thinking that allows for paradigm shifts serves as an indispensable soil.

Metaphorical 'dojo' (soil).

絶対的な他者との共生を考える時、自己の相対化は不可欠なプロセスである。

When considering coexistence with the absolute 'other,' the relativization of the self is an indispensable process.

Using 'soutaika' (relativization).

Collocations courantes

不可欠な要素

不可欠な役割

不可欠な条件

不可欠な栄養素

不可欠な存在

不可欠なスキル

不可欠なインフラ

不可欠なプロセス

不可欠な機能

不可欠な知識

Phrases Courantes

必要不可欠である

— To be absolutely necessary. A very formal way to state a requirement.

その対策は必要不可欠である。

〜にとって不可欠だ

— To be indispensable for [someone/something]. Used to specify the target.

子供にとって遊びは不可欠だ。

不可欠な部分

— An indispensable part. Used to describe a component of a whole.

これは計画の不可欠な部分だ。

不可欠なステップ

— An indispensable step. Used for processes and procedures.

確認は不可欠なステップです。

不可欠なリソース

— Indispensable resources. Often used in business or management.

人材は不可欠なリソースだ。

不可欠なツール

— Indispensable tool. Used for software or physical equipment.

このソフトは仕事に不可欠なツールだ。

不可欠なデータ

— Indispensable data. Used in research and analysis.

不可欠なデータを収集する。

不可欠な才能

— Indispensable talent. Used for specific skills in a person.

彼には不可欠な才能がある。

不可欠な安全策

— Indispensable safety measure. Used in risk management.

ヘルメットは不可欠な安全策だ。

不可欠な協力

— Indispensable cooperation. Used in teamwork.

皆様の不可欠な協力をお願いします。

Souvent confondu avec

不可欠な vs 必要 (Hitsuyo)

Hitsuyo is general 'need'; Fukaketsu is absolute 'indispensable'.

不可欠な vs 必須 (Hissu)

Hissu is often 'mandatory' (rules); Fukaketsu is 'essential' (logic/nature).

不可欠な vs 重要 (Juyo)

Juyo is 'important' but not necessarily 'cannot do without'.

Expressions idiomatiques

"なくてはならない"

— Must have; cannot do without. A very common idiomatic phrase similar to fukaketsu.

彼はこの会社になくてはならない存在だ。

Neutral

"欠かせない存在"

— An existence that cannot be lacked. Used for people who are vital to a group.

彼女はチームに欠かせない存在だ。

Neutral

"命綱となる"

— To become a lifeline. Used for something absolutely vital for survival.

この契約は会社にとって命綱となる不可欠なものだ。

Metaphorical

"喉から手が出るほど"

— To want something so badly (literally 'hand coming out of the throat'). Not the same as fukaketsu, but often used when something is desired because it's considered indispensable.

その技術は不可欠で、喉から手が出るほど欲しい。

Idiomatic

"背に腹はかえられない"

— Necessity knows no law; you can't sacrifice your back to save your belly. Used when a difficult choice is made because of necessity.

不可欠な経費なので、背に腹はかえられない。

Proverb

"衣食足りて礼節を知る"

— Only when basic needs (food/clothing) are met can people care about manners. Implies food/clothes are fukaketsu for civilization.

衣食は人間にとって不可欠なものだ。

Proverb

"死活問題"

— A matter of life and death. Used for something that is absolutely indispensable for survival.

この予算削減は、我々にとって死活問題だ。

Formal

"目に入れても痛くない"

— The apple of one's eye. Used for someone so precious they are 'indispensable' to happiness.

孫は彼にとって不可欠な喜びだ。

Idiomatic

"一事が万事"

— One thing tells all. Implies that small 'indispensable' details reflect the whole.

細部への配慮が不可欠なのは、一事が万事だからだ。

Proverb

"必要は発明の母"

— Necessity is the mother of invention. Implies that needing something 'fukaketsu' leads to creation.

不可欠なものを求めて発明が生まれる。

Proverb

Facile à confondre

不可欠な vs 不可欠 (Fukaketsu)

Often confused with 'hissu' (必須).

Fukaketsu refers to something that is logically or naturally needed for a whole to exist. Hissu refers to something required by a rule or authority.

酸素は不可欠だ (Oxygen is indispensable). 出席は必須だ (Attendance is mandatory).

不可欠な vs 必要 (Hitsuyo)

General word for need.

Hitsuyo can be used for small, replaceable things. Fukaketsu implies that without it, the goal is impossible.

ペンが必要だ (I need a pen). 信頼は不可欠だ (Trust is indispensable).

不可欠な vs 欠かせない (Kakasenai)

Same meaning.

Kakasenai is a verb phrase, whereas Fukaketsu is a na-adjective. Kakasenai is more common in spoken Japanese.

笑顔は欠かせない (A smile is essential).

不可欠な vs 肝要 (Kan'yo)

Both mean very important.

Kan'yo is much more formal and slightly archaic, often used in moral or philosophical advice.

誠実さが肝要だ (Sincerity is vital).

不可欠な vs 重要 (Juyo)

Both indicate significance.

Juyo indicates that something has high value or impact, but you might still be able to function without it. Fukaketsu means you cannot function without it.

重要な会議 (An important meeting).

Structures de phrases

[Noun]は[Noun]に不可欠です。

水は生活に不可欠です。

[Goal]ためには、[Noun]が不可欠だ。

合格するためには、勉強が不可欠だ。

[Noun]は[Target]にとって不可欠な要素だ。

信頼は友人にとって不可欠な要素だ。

〜において、…が不可欠な役割を果たす。

教育において、教師が不可欠な役割を果たす。

〜を担保するには、…が不可欠な要件である。

自由を担保するには、法が不可欠な要件である。

〜の過程において、…は不可欠な契機となる。

成長の過程において、失敗は不可欠な契機となる。

[Abstract Noun]には、[Abstract Noun]が不可欠な前提である。

民主主義には、多義性が不可欠な前提である。

〜を模索する上で、…は不可欠な要諦だ。

平和を模索する上で、対話は不可欠な要諦だ。

Famille de mots

Noms

欠乏 (Ketsubo - Deficiency)

欠如 (Kejyo - Lack)

可能性 (Kanousei - Possibility)

不可欠性 (Fukaketsusei - Indispensability)

Verbes

欠く (Kaku - To lack)

欠ける (Kakeru - To be chipped/lacking)

許可する (Kyoka suru - To permit)

Adjectifs

欠かせない (Kakasenai - Indispensable/potential form)

可能な (Kanou na - Possible)

不可な (Fuka na - Impossible/unacceptable)

Apparenté

必須 (Hissu)

必要 (Hitsuyo)

重要 (Juyo)

肝心 (Kanjin)

肝要 (Kan'yo)

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Comment l'utiliser

frequency

High in formal/academic/professional contexts; Low in casual street slang.

Erreurs courantes

Using 'fukaketsu' for wanting a snack. → お菓子が必要だ (I need a snack).
Fukaketsu is too formal and strong for trivial desires. It sounds like you will die without the snack.
Saying '不可欠要素' in a normal sentence. → 不可欠な要素 (An indispensable element).
Fukaketsu is a na-adjective. You must use 'na' to connect it to a noun unless it's a fixed compound word.
Using 'wo' with fukaketsu. → 協力が不可欠だ (Cooperation is indispensable).
Fukaketsu is an adjective, not a verb. It takes the subject marker 'ga', not the object marker 'wo'.
Confusing 'fukaketsu' with 'hissu' for a school rule. → この授業は必須です (This class is mandatory).
Rules and regulations use 'hissu'. Natural or logical needs use 'fukaketsu'.
Using 'zettai ni fukaketsu' in formal writing. → 不可欠である (Is indispensable).
Fukaketsu already means 'absolute necessity,' so adding 'zettai' is often seen as redundant in high-level writing.

Astuces

Formal Contexts

Use 'fukaketsu' in business reports or academic essays to show that an element is a core requirement. It makes your argument sound more logical and grounded.

Pair with 'Ni Totte'

When you want to say something is essential *for* someone, always use 'にとって'. Example: 'Watashi ni totte fukaketsu' (Indispensable for me).

Absolute Necessity

Only use this word when there is no alternative. If there is a substitute, 'hitsuyo' (necessary) is a more accurate word choice.

Kanji Recognition

Learn the kanji '欠' (ketsu) in other words like 'kesseki' (absence) or 'ketten' (defect) to strengthen your memory of its 'missing/lacking' meaning.

Natural Alternatives

In casual speech, switch to 'kakasenai' (欠かせない). It conveys the same 'must-have' feeling but sounds much more like a native speaker in a café.

Compound Power

Use '必要不可欠' (hitsuyo-fukaketsu) when you want to leave no doubt that something is required. It's a powerful phrase in persuasive writing.

Interview Tip

Describe a 'fukaketsu na skill' you possess that the company needs. It shows you understand the core requirements of the role.

Scientific Terms

Remember '不可欠アミノ酸' (essential amino acids) as a fixed term. It helps you remember that the word applies to biological needs too.

The 'Wa' (Harmony)

In Japan, being a 'fukaketsu' part of a team means you are reliable. Strive to be a 'fukaketsu na sonzai' in your community.

Check the 'Na'

Always check if you need the 'na'. If it's before a noun, add it. If it's at the end of the sentence, use 'da' or 'desu'.

Mémorise-le

Moyen mnémotechnique

Think of the three parts: FU (No) + KA (Can) + KETSU (Lack). It is 'No-Can-Lack.' If you can't lack it, it's indispensable!

Association visuelle

Imagine a car without a wheel. The wheel is 'fukaketsu.' Without it, the car is just a heavy box.

Word Web

Oxygen Water Trust Internet Passport Skill Effort Sleep

Défi

Write three things that are 'fukaketsu' for your daily routine using the pattern: '[Noun] wa watashi ni totte fukaketsu desu.'

Origine du mot

The word is a Sino-Japanese compound (Kango). It appeared in the modern era as Japanese scholars translated Western philosophical and scientific concepts into Japanese using Kanji.

Sens originel : Not possible to lack.

Japonic / Sino-Japanese.

Contexte culturel

Be careful not to use 'fukaketsu' to describe people in a way that sounds like they are just 'tools' or 'parts' unless you are emphasizing their value to a team.

Similar to how 'indispensable' sounds more sophisticated than 'needed' in English, 'fukaketsu' signals higher education or professional status in Japan.

Used in Japanese translations of the UN Declaration of Human Rights. Commonly found in scientific papers regarding 'Essential Amino Acids' (不可欠アミノ酸). A frequent term in business leadership books by authors like Kazuo Inamori.

Pratique dans la vie réelle

Contextes réels

Business Meeting

この戦略は不可欠です。
不可欠なリソースの確保。
協力は不可欠な要素だ。
不可欠なスキルセット。

Science/Health

不可欠な栄養素。
生命維持に不可欠。
不可欠なプロセス。
不可欠アミノ酸。

Legal/Politics

不可欠な権利。
不可欠な条件。
存続に不可欠。
不可欠な要件。

Education

不可欠な知識。
学習に不可欠な道具。
成功に不可欠な努力。
不可欠なステップ。

Personal Relationships

君は僕に不可欠だ。
信頼は不可欠なもの。
不可欠な存在。
会話は不可欠だ。

Amorces de conversation

"仕事で一番不可欠なスキルは何だと思いますか？"

"あなたにとって、毎日の生活に不可欠なものは何ですか？"

"成功するために、努力以外に何が不可欠だと思いますか？"

"今の社会で、インターネットは本当に不可欠だと思いますか？"

"良い人間関係を築くために、何が不可欠な要素だと思いますか？"

Sujets d'écriture

自分にとって不可欠な三つのものを書き、その理由を説明してください。

将来の夢を叶えるために不可欠なステップについて考えてみましょう。

もしインターネットがなくなったら、あなたの生活に不可欠なものはどう変わりますか？

あなたの仕事や勉強において、不可欠な道具やアプリは何ですか？

「幸せ」にとって、お金は不可欠な要素だと思いますか？

Questions fréquentes

10 questions

It is primarily a na-adjective (na-keiyoushi). You use '不可欠な' to modify a noun, like '不可欠な要素' (indispensable element). It can also be used as a noun in some formal contexts, but the adjective form is most common.

Yes, you can say '彼は不可欠な存在だ' (He is an indispensable presence). This is a high compliment in a professional or personal setting, meaning the person is vital to the group or your life.

Meaning-wise, they are almost identical. However, 'kakasenai' is more common in spoken, everyday Japanese, while 'fukaketsu' is more academic, formal, and written. 'Kakasenai' feels a bit warmer and more natural in conversation.

While it literally means 'necessary-indispensable,' it is a very common and accepted set phrase in Japanese used for emphasis. It's like saying 'absolutely essential' in English. It is not considered an error.

You can, but it might sound a bit stiff or dramatic. If you're talking about something like a phone or a hobby, 'kakasenai' or 'hitsuyo' is usually a better fit for a relaxed vibe.

Usually 'が' (ga) when used as a predicate: '[Noun] が不可欠だ'. When describing who it is indispensable for, use 'にとって' (ni totte).

The kanji are 不 (fu), 可 (ka), and 欠 (ketsu). Be careful with '欠'—it looks similar to '次' (next) but doesn't have the two dots on the left. It has 4 strokes.

Since '不可欠' already contains a negative (不), you don't usually negate it further. Instead, you would use '不要' (unnecessary) or '不可欠ではない' (not indispensable).

Yes, it is typically considered an N2 level word, though it frequently appears in N1 reading materials as well.

It is usually used for objects, qualities, or conditions. While you wouldn't say a feeling is 'fukaketsu,' you could say that 'love' or 'passion' is 'fukaketsu' for a happy life.

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