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B1 noun 11 min read

分解

bunkai

Practice it Examples Notes & Tips 分解 in 30 Seconds

Explanation 分解 in your Level:

At the A1 level, you don't need to use the word 分解 (bunkai) often, but you might see it on labels or in very simple hobby contexts. Think of it as 'taking things apart.' Imagine you have a toy made of blocks. If you take the blocks apart one by one, that is bunkai. At this stage, just remember that bun (分) means 'part' and kai (解) means 'to untie.' So, it's 'untying the parts.' You might hear a teacher say 'Let's break this word down' using simpler words, but bunkai is the 'grown-up' version of that. It's a useful word to recognize if you like fixing things or doing science experiments. Just remember: it's not about breaking things by mistake (that's kowasu); it's about taking them apart on purpose.

For A2 learners, 分解 (bunkai) becomes useful when describing chores or simple hobbies. If you are cleaning an air conditioner or a fan, you often have to 'disassemble' it. You might see this word in the instruction manual: '分解しないでください' (Do not disassemble). This is a very important phrase for safety! You also start to learn that Japanese verbs can be made by adding 'suru' to a noun. So, bunkai (disassembly) + suru (do) = bunkai suru (to disassemble). You can use this when talking about your hobbies, like taking apart an old radio or a computer. It sounds much more skilled and professional than just saying you 'broke' it. It shows you are doing it with a plan!

At the B1 level, you should start using 分解 (bunkai) in technical and academic contexts. This is where you move beyond just 'machines' and into 'science' and 'math.' In a B1 science context, you'll learn about how things like plastic or food 'decompose' (bunkai) in the environment. You'll also encounter 'factorization' in math class, called insu-bunkai. At this level, you should also be able to use the passive form: bunkai sareru. For example, 'This material is decomposed by bacteria.' You're also starting to see the word in news reports about technology, like 'teardown' articles of new gadgets. You should be able to distinguish bunkai from bunseki (analysis). Bunkai is the physical act; bunseki is the thinking act.

By B2, you are expected to use 分解 (bunkai) fluently in professional settings. You might use it in a business meeting to talk about 'breaking down' a complex project into smaller tasks (プロジェクトを分解する). You should also be familiar with compound nouns like bunkai-shuri (overhaul/repair by disassembly) or seibunkaisei (biodegradability). At this level, you understand the nuance that bunkai implies a systematic process. You might use it to describe linguistics—breaking down a sentence into its components (morphological analysis). You should also be comfortable using it in the context of sports analysis, where a coach 'breaks down' a player's form. The word now represents a tool for understanding complex systems by looking at their individual parts.

At the C1 level, 分解 (bunkai) is used for abstract and philosophical discussions. You might talk about the 'decomposition' of traditional social structures or the 'breakdown' of a political alliance. Here, the word takes on a more metaphorical meaning, similar to 'deconstruction' in English. You'll encounter it in high-level academic papers, perhaps in sociology or philosophy, describing how concepts are dismantled. You should also be aware of its specific uses in advanced fields like organic chemistry (molecular decomposition) or computer science (functional decomposition). Your ability to use bunkai in these varied, non-physical contexts shows a deep grasp of the word's core logic: that any complex whole is merely a sum of parts that can be examined individually.

At the C2 level, your mastery of 分解 (bunkai) allows you to use it with precision in highly specialized discourse. You can discuss the 'electrolytic decomposition' (電気分解) of rare earth elements or the 'thermal decomposition' (熱分解) of polymers in industrial engineering. You might use it in literary criticism to describe the 'deconstruction' of a narrative. At this level, you also understand the subtle interplay between bunkai and its synonyms like kaiseki or kaitai in nuanced ways. For instance, you might argue that a particular policy 'decomposes' the unity of a nation. You can also appreciate the word's role in Japanese history and education, recognizing it as a key term that bridged Western scientific concepts with Japanese thought during the Meiji era. It is no longer just a vocabulary word; it is a conceptual framework for your Japanese communication.

Practice it Examples Notes & Tips

分解 in 30 Seconds

Bunkai means disassembling machines or decomposing chemicals systematically.
It is a formal, technical term used in engineering, science, and math.
It differs from 'kowasu' (breaking) as it implies a controlled, purposeful process.
Commonly seen in instruction manuals, science labs, and gadget teardown reports.

The Japanese word 分解 (ぶんかい - bunkai) is a sophisticated and versatile term primarily used to describe the act of taking something apart into its constituent components. It functions as both a noun and a 'suru' verb. While in English we might use different words like 'disassemble' for a machine, 'decompose' for a leaf, and 'factorize' for an equation, Japanese often uses bunkai to cover all these technical bases. The nuance is inherently systematic and methodical; it is not about breaking something through violence or accident, but rather a purposeful separation of parts to understand, repair, or transform the whole.

Mechanical Context: In the world of engineering and daily maintenance, 分解 refers to the disassembly of hardware. If your watch stops working and a jeweler takes it apart to see the gears, they are performing bunkai. It is the standard term found in instruction manuals (取扱説明書) when describing how to clean a vacuum cleaner or a camera lens.
Chemical and Biological Context: In science, 分解 describes the breakdown of substances. This includes 'electrolysis' (電気分解 - denki bunkai), where water is split into hydrogen and oxygen, and 'biodegradation' (生分解 - seibunkai), where microorganisms break down organic waste. It signifies a change in state where a complex molecule becomes simpler ones.

この古い時計を分解して、中身を確認しましょう。
(Let's disassemble this old watch and check the contents.)

Beyond the physical, bunkai is used in mathematics and linguistics. In math, 'insu-bunkai' (因数分解) is the term for factorization—breaking a number or polynomial into its factors. In linguistics, one might 'bunkai' a complex sentence into its grammatical components to analyze its structure. This abstract usage highlights the word's connection to 'analysis' (分析 - bunseki), though bunkai remains more focused on the physical or structural separation of the parts themselves.

プラスチックは自然界でなかなか分解されません。
(Plastic does not easily decompose in the natural world.)

Mathematical Usage: Students in Japan encounter this word early in middle school during math class. Factorization (因数分解) is a core part of the curriculum. Here, the 'untying' (解) of the numbers (分) is literal in the logic of the calculation.

In contemporary tech culture, bunkai is also the word used for 'teardowns' of new gadgets. When a new iPhone is released and a website like iFixit takes it apart to show the internal components, Japanese tech blogs will title the article as a 'bunkai report'. This usage reinforces the idea of disassembly for the purpose of inspection or understanding. It is also used in sports analysis, such as 'breaking down' a video of a baseball swing into frame-by-frame movements to identify flaws.

最新のスマートフォンの分解動画が話題になっています。
(The teardown video of the latest smartphone is becoming a hot topic.)

To wrap up, bunkai is the go-to word for any situation where a whole is separated into its parts for a constructive or analytical reason. Whether you are a chemist, a mechanic, a math student, or a curious hobbyist, this word is essential for describing the process of looking 'under the hood' of how things are put together.

Using 分解 correctly depends on whether you are using it as a noun or a verb. As a noun, it often pairs with particles like no (の) or o (を). As a verb, it becomes 分解する (bunkai suru), meaning 'to disassemble' or 'to decompose'. Because it is a technical term, the sentences often involve objects like machines, chemicals, or mathematical expressions.

Active Voice (Transitive): When a person or an agent is doing the disassembling, use ~o bunkai suru. For example: 'I disassembled the PC' (PCを分解した). This implies a deliberate action by the subject.

エンジニアは、故障の原因を突き止めるためにエンジンを分解した。
(The engineer disassembled the engine to pinpoint the cause of the failure.)

In scientific contexts, the passive voice is extremely common. Substances 'are decomposed' by heat, light, or bacteria. In Japanese, this is 分解される (bunkai sareru). This is used when the focus is on the object being broken down rather than the agent doing it.

落ち葉は、土の中の微生物によって分解されます。
(Fallen leaves are decomposed by microorganisms in the soil.)

Noun Form with Particles: When used as a noun, it often appears in compound phrases. 'Bunkai-shuri' (分解修理) means 'overhaul' or 'repair via disassembly.' 'Bunkai-zu' (分解図) is an 'exploded-view diagram' often found in LEGO instructions or IKEA manuals.

Another important nuance is the difference between 'physical disassembly' and 'chemical decomposition.' In English, we use different verbs, but in Japanese, bunkai handles both. To clarify, you might add context. For physical items, you might say 'taking it apart into pieces' (バラバラに分解する). For chemistry, you might specify the method, like 'thermal decomposition' (熱分解 - netsu bunkai).

この家具は分解して運ぶことができます。
(This furniture can be disassembled and transported.)

Finally, consider the speed of the action. Bunkai is usually a process. If something explodes, that's not bunkai. If something slowly rots away or is carefully unscrewed, that is bunkai. The word implies a transition from a state of 'unity' to a state of 'multiplicity' where the identity of the parts becomes clearer than the identity of the whole.

光によって薬剤が分解されないよう、遮光瓶に入れてください。
(Please put it in a light-shielded bottle so the medicine isn't decomposed by light.)

Abstract/Social Usage: While less common than physical usage, you can 'bunkai' a concept or a large project. 'Project o bunkai shite kangaeru' means to break a project down into manageable tasks. This is synonymous with 'breaking it down' in a business meeting.

You are most likely to encounter 分解 (bunkai) in environments where technical precision is required. It is not a word you would typically use in a casual conversation about breaking a cookie in half, but it is ubiquitous in professional and educational settings. Understanding where it appears helps you grasp its formal and functional nature.

At the Repair Shop (修理工場): If you take your car or computer to a specialist, they might say, 'Once we perform a disassembly (bunkai), we can give you a quote.' In this context, it sounds professional and thorough. It suggests that they aren't just looking at the surface but are going deep into the mechanism.

オーバーホールの際は、全ての部品を分解して洗浄します。
(During an overhaul, we disassemble all parts and clean them.)

In schools, bunkai is a staple of the science lab. Students are taught about 'chemical decomposition' and 'electrolysis' using this term. It is one of those words that marks the transition from 'everyday Japanese' to 'academic Japanese.' If you are watching a Japanese documentary about nature or space, you will hear it frequently when experts explain how stars are formed or how waste is recycled in an ecosystem.

理科の授業で、水の電気分解の実験をしました。
(We did an experiment on the electrolysis of water in science class.)

In the Tech World (IT・テクノロジー): Programmers and systems analysts use bunkai when talking about 'decomposing' a large system into smaller modules or microservices. It is used to describe the logical separation of functions. In hardware reviews, 'bunkai-shashin' (disassembly photos) are high-traffic content for enthusiasts who want to see the chips and boards inside a new console.

You will also hear it in the context of recycling and environmentalism. Japan has strict rules about garbage disposal. Items like air conditioners or washing machines must be 'disassembled' (bunkai) at a designated plant to recover precious metals. Labels on products might say 'Easily disassemblable' (分解しやすい) to indicate they are eco-friendly.

リサイクルを容易にするため、分解しやすい設計になっています。
(It is designed to be easily disassembled to facilitate recycling.)

Finally, in the world of sports and martial arts, bunkai (often spelled in romaji even in English) refers to the analysis of 'kata' (forms). A practitioner takes a complex movement and 'breaks it down' to explain the practical application of each block and strike. This is a rare case where the Japanese word is used directly in English-speaking karate dojos worldwide.

空手の形の分解を学ぶことで、技の意味がわかります。
(By learning the 'bunkai' of karate kata, you understand the meaning of the techniques.)

At the Hospital (病院): Doctors might use it when talking about how the body processes medicine. 'The liver breaks down the alcohol' (肝臓がアルコールを分解する). It describes the metabolic process of turning a complex chemical into something the body can excrete or use.

While 分解 (bunkai) is a straightforward word, English speakers often trip up because Japanese has several words for 'breaking' or 'taking apart' that aren't interchangeable. Using bunkai in the wrong context can make you sound overly technical or just plain confusing.

Mistake 1: Confusing Bunkai with Kowasu (壊す): If you say 'I bunkai-ed my phone' when you actually dropped it and the screen cracked, people will think you took out a screwdriver and carefully removed every screw. 壊す (kowasu) is for accidental or destructive breaking. 分解 (bunkai) is for constructive or analytical disassembly.

❌ スマホを分解してしまった (落として壊したとき)
✅ スマホを壊してしまった
(Use 'kowashite' for accidental damage.)

Mistake 2: Confusing Bunkai with Bunseki (分析). In English, we often say 'break it down' to mean 'analyze it.' In Japanese, if you want to analyze data or a situation, you should use 分析 (bunseki). While bunkai can be used for abstract things, it usually implies a structural breakdown (like a sentence or a project), whereas bunseki is for finding patterns, causes, or meanings in data.

Mistake 3: Overusing it for simple actions: If you are taking a LEGO set apart to put it back in the box, bunkai is fine but sounds a bit serious. Kids might just say 'bara-bara ni suru' (make it into pieces). Using bunkai for a sandwich or a puzzle feels unnaturally formal.

❌ サンドイッチを分解して食べます。
✅ サンドイッチを分けて食べます。
(Unless you are a food scientist analyzing the layers, use 'wakete'.)

Mistake 4: Particle choice. When a substance decomposes naturally (like a biodegradable bag), beginners often use o bunkai suru (active). But nature doesn't always have a clear subject. It's better to use bunkai sareru (is decomposed) or bunkai ga susumu (decomposition progresses).

❌ この袋は自然が分解します。
✅ この袋は自然界で分解されます。
(The passive form is more natural for environmental processes.)

Mistake 5: Confusing with 'Kaitai' (解体): If you are talking about tearing down a house or a massive ship, use 解体 (kaitai). If you use bunkai for a building, it sounds like you are carefully unscrewing the skyscraper piece by piece like a watch, which is physically impossible.

By keeping these distinctions in mind, you'll avoid the 'uncanny valley' of Japanese where your grammar is correct but your word choice makes the situation sound far more scientific or far more destructive than it actually is. Stick to bunkai for machines, chemistry, math, and detailed structural analysis.

To truly master 分解 (bunkai), you must understand the words that live in its neighborhood. Japanese is rich with terms for 'breaking' and 'separating,' each with a specific flavor and domain. Comparing them will help you choose the most precise word for your needs.

分解 (Bunkai) vs. 分析 (Bunseki): Bunkai is about the physical or structural 'taking apart.' Bunseki is 'analysis.' You bunkai a clock to see the gears; you bunseki the data to see why the clock is slow. Bunkai is the 'how,' and Bunseki is the 'why' or 'what it means.'

機械を分解して、故障の原因を分析する。
(Disassemble the machine and analyze the cause of the failure.)

分解 (Bunkai) vs. 解体 (Kaitai): Kaitai is used for large-scale demolition. Think buildings, old ships, or even butchering a whole tuna (maguro no kaitai). Bunkai is for smaller, more precise objects. You bunkai a laptop; you kaitai a warehouse.

Another interesting comparison is with 溶解 (yokai), which means 'dissolving.' While bunkai is a chemical breakdown of the molecule itself, yokai is just a physical change where a solid becomes liquid in a solvent (like sugar in water). If the sugar stays sugar but is just floating in water, it's yokai. If you burn the sugar and it turns into carbon and water vapor, that's bunkai.

砂糖が水に溶解するのと、熱で分解するのは別です。
(Sugar dissolving in water and decomposing by heat are different.)

分解 (Bunkai) vs. 腐敗 (Fuhai): Both can mean 'decomposition' in biology. However, 腐敗 (fuhai) specifically means 'rotting' or 'putrefaction'—it has a negative, smelly connotation. Bunkai is the neutral scientific term for the process. A scientist says 'bunkai'; a person smelling an old fridge says 'fuhai.'

Lastly, consider 解析 (kaiseki). This is often used in high-level math or computer science (e.g., parsing code). While bunkai is taking things apart, kaiseki is interpreting the structure. In a sentence, you bunkai the words to see the grammar, and you kaiseki the meaning to understand the nuance.

Summary Table: - 分解 (Bunkai): General disassembly / decomposition. - 解体 (Kaitai): Large-scale demolition / butchery. - 分析 (Bunseki): Data/logical analysis. - 解析 (Kaiseki): Parsing / deep interpretation. - 壊す (Kowasu): To break/damage (general).

How Formal Is It?

Fun Fact

The word 'Bunkai' is used globally in Karate to describe the application of kata. It literally means 'breaking down' the movements to understand their combat meaning.

Pronunciation Guide

UK /buŋkaɪ/

US /buŋkaɪ/

Flat pitch (Heiban style), meaning the pitch stays relatively constant throughout the word.

Rhymes With

Sunkai (survey) Zenkai (full power) Mankai (full bloom) Genkai (limit) Tenkai (expansion) Kinkai (gold bar) Shinkai (deep sea) Bankai (recovery)

Common Errors

Pronouncing 'bun' like the English bread roll 'bun'. It should be 'boon'.
Making the 'n' sound too heavy like a Western 'n'. It's a soft nasal sound.
Stressing the first syllable. Japanese is pitch-accented, not stress-accented.
Misreading the kanji as 'bun-ge' or 'bun-kai' with a hard 'k'.
Confusion with 'bunsei' (analysis).

Difficulty Rating

Reading 3/5

Kanji are common but require middle-school level knowledge.

Writing 4/5

The kanji '解' is slightly complex for beginners.

Speaking 2/5

Pronunciation is simple and flat.

Listening 2/5

Clear sounds, easily distinguishable from other words.

What to Learn Next

Prerequisites

分ける解く修理部品機械

Learn Next

分析解析解体合成組み立て

Advanced

加水分解熱重量分析モジュール化構造主義

Grammar to Know

Suru-verbs

分解する、分解した、分解しよう。

Passive Voice

分解される、分解されました。

Potential Form

分解できる、分解できない。

Compound Nouns

分解修理 (Noun + Noun).

Te-form for means

分解して修理する。

Examples by Level

おもちゃを分解します。

I take the toy apart.

Simple noun + o + verb structure.

これは分解できますか？

Can this be taken apart?

Potential form of bunkai-suru.

パズルを分解した。

I took the puzzle apart.

Past tense of bunkai-suru.

分解はやめてください。

Please stop taking it apart.

Noun + wa + yamete kudasai.

時計を分解するのは楽しい。

Taking apart a watch is fun.

Using 'no' to turn the verb into a noun phrase.

ペンを分解してみよう。

Let's try taking the pen apart.

te-form + miyou (try doing).

分解のやり方がわからない。

I don't know how to take it apart.

Noun + no + yarikata (way of doing).

父はカメラを分解した。

My father took the camera apart.

Subject + wa + object + o + verb.

掃除のために、扇風機を分解した。

I disassembled the fan for cleaning.

tame ni (for the purpose of).

この机は分解して運べます。

This desk can be disassembled and carried.

te-form for connecting actions.

説明書を読んで分解してください。

Please read the manual and disassemble it.

te-form + kudasai.

勝手に分解してはいけません。

You must not disassemble it without permission.

te wa ikemasen (prohibition).

分解した部品をなくさないで。

Don't lose the disassembled parts.

nai de (negative request).

古いパソコンを分解して中を見た。

I disassembled an old PC and looked inside.

Sequential actions with te-form.

分解するのは簡単だが、組み立てるのは難しい。

Disassembling is easy, but assembling is hard.

Contrast using 'ga' (but).

分解修理が必要です。

A repair involving disassembly is necessary.

Compound noun (bunkai-shuri).

プラスチックは自然界で分解されにくい。

Plastic is hard to decompose in nature.

Passive potential negative: sareru + nikui.

数学の授業で因数分解を習った。

I learned factorization in math class.

Specific term: insu-bunkai.

この薬品は熱で分解されます。

This chemical is decomposed by heat.

Passive form: sareru.

光によって分解が進むことがあります。

Decomposition may progress due to light.

ni yotte (by/due to).

複雑な問題を小さく分解して考えよう。

Let's break down complex problems into smaller ones and think.

Abstract usage of bunkai.

微生物が有機物を分解する。

Microorganisms decompose organic matter.

Subject + ga + object + o + verb.

この図はエンジンの分解図です。

This diagram is an exploded view of the engine.

Compound noun: bunkai-zu.

彼は壊れた時計を分解して直した。

He disassembled the broken watch and fixed it.

te-form for means/method.

生分解性プラスチックの利用が広がっている。

The use of biodegradable plastic is spreading.

Compound adjective: seibunkaisei.

水の電気分解によって水素が発生する。

Hydrogen is generated by the electrolysis of water.

Scientific term: denki bunkai.

プロジェクトのタスクを詳細に分解する。

Break down the project tasks in detail.

Business context.

この物質は高温で急速に分解を始める。

This substance begins to decompose rapidly at high temperatures.

o-hajimeru (begin doing).

文を文法要素に分解して解析する。

Decompose a sentence into grammatical elements and analyze it.

Linguistic context.

最新機種の分解レポートをネットで読んだ。

I read a teardown report of the latest model online.

Tech industry term: bunkai report.

過度なストレスは精神を分解させる恐れがある。

Excessive stress may threaten to break down the psyche.

Causative form: saseru.

触媒を使うことで、有害物質の分解を促進する。

By using a catalyst, the breakdown of harmful substances is promoted.

koto de (by means of).

社会構造の分解が、孤独死の一因となっている。

The breakdown of social structures is one cause of solitary deaths.

Sociological abstract usage.

理論を構成要素に分解し、それぞれの妥当性を検証する。

Decompose the theory into its constituent elements and verify the validity of each.

Verification and analysis context.

放射性物質の自然分解には長い年月を要する。

The natural decay (decomposition) of radioactive materials requires many years.

Scientific/Environmental context.

組織が肥大化しすぎて、機能分解が必要だ。

The organization has grown too large and needs functional decomposition.

Management/Systems theory.

伝統的な家族観の分解は避けられない傾向だ。

The disintegration of traditional views on family is an unavoidable trend.

Metaphorical usage.

酵素の働きによって、食物が効率よく分解される。

Food is efficiently broken down by the action of enzymes.

Biological process.

このポリマーは特定の波長の光で分解を誘導できる。

This polymer's decomposition can be induced by light of a specific wavelength.

Advanced science.

過去の記憶を分解して、新しい物語を再構築する。

Deconstruct past memories and reconstruct a new story.

Creative/Psychological context.

ポスト構造主義は、テクストの分解と再構成を重視する。

Post-structuralism emphasizes the deconstruction and reconstruction of texts.

Literary theory context.

細胞内のリソソームは、不要なタンパク質を分解する役割を担う。

Lysosomes within cells play the role of breaking down unnecessary proteins.

Specialized biology.

当該化合物の熱分解挙動を熱重量分析で評価した。

The thermal decomposition behavior of the compound was evaluated by thermogravimetric analysis.

Academic research paper style.

権力の分解は、民主主義を維持するための不可欠なプロセスである。

The decomposition (separation) of power is an essential process for maintaining democracy.

Political science context.

ソフトウェアのモジュール分解における凝集度と結合度のバランスを検討する。

Examine the balance between cohesion and coupling in software module decomposition.

Advanced software engineering.

宇宙における星間物質の分解と生成のサイクルを解明する。

Elucidate the cycle of decomposition and generation of interstellar matter in the universe.

Astrophysics context.

法解釈において、条文を分解して論理的整合性を問う。

In legal interpretation, decompose the articles and question the logical consistency.

Legal context.

意識の分解不可能性という難問に直面している。

Facing the hard problem of the indecomposability of consciousness.

Philosophy of mind.

Synonyms

解体分析解析崩壊溶解

Antonyms

合成組み立て

Common Collocations

分解掃除

因数分解

電気分解

分解図

生分解性

分解能

熱分解

再分解

機能分解

分解作業

Common Phrases

バラバラに分解する

— To take something completely apart into individual pieces.

彼はラジオをバラバラに分解した。

分解して考える

— To break down a problem and think about it logically.

一度分解して考え直しましょう。

自然に分解される

— To decompose naturally (biodegrade).

この素材は土の中で自然に分解される。

分解の逆は組み立て

— The opposite of disassembly is assembly.

分解の逆は組み立てであることを忘れないで。

分解を試みる

— To attempt a disassembly.

素人が分解を試みるのは危険だ。

完全に分解する

— To disassemble or decompose something entirely.

有害物質を完全に分解する技術。

分解が容易だ

— Easy to disassemble.

この椅子は分解が容易だ。

分解を禁止する

— To prohibit disassembly.

メーカーは分解を禁止している。

分解スキル

— Disassembly skills (often used in gaming or DIY).

分解スキルを磨く。

分解の手順

— The steps/procedure for disassembly.

分解の手順を確認する。

Often Confused With

分解 vs 壊す (Kowasu)

Kowasu is for breaking/damaging; Bunkai is for taking apart systematically.

分解 vs 分析 (Bunseki)

Bunseki is logical analysis; Bunkai is physical/structural separation.

分解 vs 解体 (Kaitai)

Kaitai is for large-scale demolition (buildings/ships); Bunkai is for smaller machines.

Idioms & Expressions

"形骸を分解する"

— To dismantle a mere shell or shadow of something.

古い組織の形骸を分解する。

Literary

"要素分解"

— Breaking something down into its core elements (business/logic).

売上を要素分解して分析する。

Business

"因数分解のように解く"

— To solve a problem as logically as a math equation.

人生の悩みを因数分解のように解く。

Metaphorical

"バラバラ分解"

— A state of being completely taken apart (often used by children).

おもちゃがバラバラ分解だ！

Child-friendly

"精神の分解"

— Mental breakdown (metaphorical).

極限状態で精神の分解を招く。

Psychological

"分解修理の鬼"

— Someone obsessed with taking things apart and fixing them.

彼は分解修理の鬼だ。

Colloquial

"光分解"

— Photolysis (chemical breakdown by light).

このプラスチックは光分解する。

Technical

"加水分解"

— Hydrolysis (breakdown by water).

スニーカーの底が加水分解した。

Technical

"自己分解"

— Self-decomposition or self-destruction (biological/chemical).

細胞が自己分解を始める。

Scientific

"分解の美学"

— The aesthetic appreciation of internal components.

時計の分解の美学に惹かれる。

Artistic

Easily Confused

分解 vs 解析 (Kaiseki)

Both involve 'breaking down'.

Kaiseki is used for parsing data or signals (like DNA or code), while Bunkai is for physical or basic structural breakdown.

DNAを解析する vs 水を分解する。

分解 vs 溶解 (Yokai)

Both involve things 'disappearing' into a medium.

Yokai is physical dissolving (sugar in water); Bunkai is chemical breakdown (water into gas).

塩を溶解する vs ゴミを分解する。

分解 vs 腐敗 (Fuhai)

Both mean 'decomposition'.

Fuhai specifically means rotting/spoiling with a bad smell; Bunkai is the neutral scientific term.

肉が腐敗する vs 有機物が分解される。

分解 vs 解散 (Kaisan)

Both mean 'breaking up'.

Kaisan is for groups of people (bands, meetings); Bunkai is for physical objects or substances.

バンドが解散する vs 時計を分解する。

分解 vs 破壊 (Hakai)

Both involve things being in pieces.

Hakai is total destruction; Bunkai is orderly disassembly.

建物を破壊する vs 機械を分解する。

Sentence Patterns

[Object] を分解します。

時計を分解します。

[Object] を分解して [Action]。

掃除機を分解して洗います。

[Object] は [Agent] によって分解される。

ゴミは微生物によって分解される。

[Abstract] を [Components] に分解する。

問題を要素に分解する。

[Phenomenon] は [Factor] の分解を招く。

不況は社会の分解を招く。

[Object] は分解しやすい。

この棚は分解しやすい。

[Object] を分解しないでください。

電池を分解しないでください。

[Condition] で分解が進む。

高温多湿で分解が進む。

Word Family

Nouns

分解者 (Decomposer - biology)

因数分解 (Factorization)

電気分解 (Electrolysis)

分解図 (Exploded view)

Verbs

分解する (To disassemble/decompose)

分解される (To be disassembled/decomposed)

Adjectives

生分解性の (Biodegradable)

分解可能な (Disassemblable/Decomposable)

分ける (To divide)

解く (To untie/solve)

解体 (Demolition)

分析 (Analysis)

解析 (Parsing)

How to Use It

frequency

High (especially in technical/instructional domains)

Common Mistakes

Using 'bunkai' for a broken leg. → Kinsetsu (骨折)
Bunkai is for systematic disassembly, not medical fractures.
Using 'bunkai' for a broken heart. → Shitsuren (失恋)
Bunkai is technical; it doesn't apply to emotions.
Saying 'Computer o bunkai shita' when you just turned it off. → Computer o kitta (切った)
Bunkai means physically taking the hardware apart.
Confusing 'bunkai' with 'bunsho' (sentence). → Bunkai (分解)
They sound similar but are completely different. Bunsho is a sentence; Bunkai is disassembly.
Using 'bunkai' for cutting hair. → Kiru (切る)
Hair is not a machine or a chemical compound to be 'disassembled'.

Tips

Manual Reading

When you see '分解禁止' (Bunkai Kinshi) on a product, it means 'Disassembly Prohibited'. Do not open it or you'll void the warranty!

Kanji Hint

The first kanji 分 means 'minutes' or 'parts'. The second 解 means 'solve' (as in 'kotae'). Think: Solving by looking at the parts.

Decomposition

In chemistry, 'bunkai' is a reaction where one compound splits into two or more substances.

Factorization

If you are studying for a Japanese math test, 'insu-bunkai' (因数分解) is one of the most important terms to know.

Karate Context

If you practice Karate, 'bunkai' is the study of how kata movements are used in real combat.

Eco-friendly

Products labeled '生分解性' are better for the earth because they break down naturally.

Teardowns

Search for 'iPhone 分解' on YouTube to see high-quality disassembly videos in Japanese.

Untying Horns

The kanji 解 (kai) shows a horn (角) and a knife (刀) and an ox (牛). It literally means 'butchering/untying an ox'.

Passive Form

Nature 'decomposes' things, so 'bunkai sareru' (is decomposed) is very common in biology.

Bara-bara

Pair 'bunkai' with the onomatopoeia 'bara-bara' to emphasize something being in many pieces.

Memorize It

Mnemonic

Think of a 'Bun' (part) and a 'Kai' (key/solution). You need to separate the **Bun** to find the **Kai** (solution) to how it works.

Visual Association

Imagine an exploded-view diagram of a LEGO set where all the parts are floating in the air, perfectly organized.

Word Web

Parts Screwdriver Chemistry Math Microbes Repair Teardown Logic

Challenge

Go to a Japanese tech blog and search for '分解レポート'. Try to identify the parts of the gadget being described.

Word Origin

Composed of two Sino-Japanese (Kan-on) characters. '分' (bun) originates from the image of a knife dividing something in two. '解' (kai) originates from the image of hands untying the horns of an ox, meaning to loosen or solve.

Original meaning: To divide and untie; to separate a whole into its parts to understand or fix it.

Sino-Japanese (Kanji)

Cultural Context

No specific sensitivities; it's a technical and neutral term.

English speakers use 'take apart' informally, but Japanese speakers use 'bunkai' in both professional and hobbyist contexts.

iFixit (known as 'Bunkai site' in Japan) Insu-bunkai (the bane of Japanese middle schoolers) Karate Bunkai tutorials

Practice in Real Life

Real-World Contexts

Repair Shop

分解修理をお願いします。
分解して確認します。
分解図はありますか？
分解に時間がかかります。

Science Lab

電気分解の実験。
熱で分解される。
微生物による分解。
化学分解が起こる。

Math Class

因数分解を解く。
式を分解する。
共通因数で分解する。
分解の公式。

Recycling

分解して分別する。
生分解性プラスチック。
分解が容易な設計。
リサイクル工場での分解。

Business

タスクを分解する。
問題を要素分解する。
機能を分解する。
コストを分解して見る。

Conversation Starters

"「機械を分解して中を見るのは好きですか？」 (Do you like taking machines apart to see inside?)"

"「最近、何かを分解修理したことはありますか？」 (Have you disassembled and repaired anything lately?)"

"「生分解性プラスチックについてどう思いますか？」 (What do you think about biodegradable plastics?)"

"「因数分解は得意でしたか？」 (Were you good at factorization?)"

"「この家具、分解して運ぶのは大変そうですね。」 (It looks like it'll be hard to disassemble and carry this furniture.)"

Journal Prompts

今日、分解した（あるいは分解したかった）ものについて書いてください。

複雑な問題を分解して解決した経験はありますか？

分解修理の魅力は何だと思いますか？

自然界の分解サイクルについて、あなたの考えを述べてください。

もし自分の性格を要素分解するとしたら、どんなパーツがありますか？

Frequently Asked Questions

10 questions

Usually, no. For a relationship, use 'Hatan' (破綻 - breakdown) or 'Kaiso' (解消 - dissolution). 'Bunkai' sounds like you are taking the people apart physically.

'Bunkai' is the general word. 'Insu-bunkai' is the specific term for mathematical factorization (factorizing numbers or variables).

Yes, to mean 'breaking down' a project or goal into smaller, actionable tasks. It sounds very logical and strategic.

Use 'Seibunkaisei' (生分解性). For example, 'Seibunkaisei plastic' (biodegradable plastic).

In a scientific sense (digestion), yes. In a cooking sense (chopping), no. Use 'Kiru' (cut) or 'Wakeru' (divide) for food.

Not every day, unless you are a mechanic, scientist, or student. But you will see it often on labels and instructions.

It is an 'exploded-view diagram' showing how parts of a machine fit together. Common in manuals.

Yes, taking a puzzle apart is 'bunkai'. But for a jigsaw puzzle, people often just say 'bara-bara ni suru'.

Yes, you can say 'bunkai suru' (to disassemble/decompose).

It is 'electrolysis'—breaking down a substance using electricity.