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A1 noun #2,663 le plus courant 8 min de lecture

仮定

katei
Entraîne-toi Exemples Notes et astuces 仮定 en 30 secondes
Explication 仮定 in your Level:
At the A1 level, you don't need to use the word 'Katei' (仮定) itself very often, but you are learning the idea behind it. When you say 'If' using 'moshimo' or the '~tara' form, you are making a simple assumption. 'Katei' is just the big, formal name for that 'If'. Imagine you are playing a game and you say, 'If I am the king, you are the knight.' That 'If' is a 'Katei'. It's like a 'pretend' rule for a moment. In your Japanese studies, you might see this word in your textbook when the teacher explains how to use 'if' sentences. Just remember: Katei = The 'If' part of a sentence. It's a useful word to know when you want to talk about things that are not real right now but could be in a story or a plan.
At the A2 level, you can start to recognize 'Katei' (仮定) as a formal way to say 'assumption'. You might hear it in a classroom or see it in a simple news report. It's often used when people are talking about plans. For example, 'Let's assume we have 10 people' (10人いると仮定しましょう). This is a bit more grown-up than just saying 'moshimo'. You should also know that 'Katei' has some 'twin' words that sound the same but mean different things, like 'Katei' (process) and 'Katei' (curriculum). At this level, focus on the 'If' meaning. If you see '仮' (temporary) and '定' (fixed), you know it's the 'assumption' version. It's a great word to use when you want to sound a little more serious about your ideas.
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By B1, you should be comfortable using 'Katei' (仮定) in more structured ways. You will encounter it in the phrase 'Katei-kei' (仮定形), which is the conditional form of verbs (like 'yomeba' or 'sureba'). Understanding that this grammar is literally called the 'Assumption Form' helps you realize its purpose: it sets a condition. You can also start using the verb 'Katei suru' (to assume). For instance, in a business meeting or a school project, you might say, 'Assuming this plan fails, what is the next step?' (この計画が失敗すると仮定して、次のステップは何ですか？). This shows you can think logically and prepare for different outcomes. It's a key word for moving from basic conversation to more analytical Japanese.
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At the B2 level, 'Katei' (仮定) becomes a vital tool for debate and complex explanation. You should be able to distinguish it from similar words like 'Soutei' (supposition for planning) and 'Suisoku' (inference based on clues). You will use 'Katei' to build logical frameworks. For example, 'Based on the assumption that the population will decrease...' (人口が減少するという仮定に基づき...). You'll also encounter the phrase 'Katei no hanashi' (hypothetical talk), which is used to discuss 'what-if' scenarios without committing to them as facts. This is very common in political discussions or deep conversations about life. You should also be aware of the nuance that 'Katei' is neutral—it doesn't imply you believe the assumption is true, just that you are using it for the sake of the argument.
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At the C1 level, you use 'Katei' (仮定) with precision in academic, legal, or highly technical contexts. You understand its role in the 'Scientific Method' and how it differs from 'Kasetsu' (hypothesis). You can handle complex sentences like 'Stacking assumptions upon assumptions leads to a flawed conclusion' (仮定に仮定を重ねることは、誤った結論を導くことになる). You are also sensitive to the register; you know that 'Katei' is the appropriate term for a formal paper, whereas 'Kari ni' might be used as an adverb in a lecture. You can discuss the philosophical implications of 'Katei'—how our understanding of reality is often built on unverified assumptions. Your ability to challenge someone's 'Katei' politely in a professional setting is a mark of high-level fluency.
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At the C2 level, 'Katei' (仮定) is a concept you can manipulate with nuance and rhetorical skill. You understand its historical development in the Japanese language, particularly how it was used to translate Western philosophical and mathematical concepts during the Meiji era. You can use it in abstract discussions about linguistics, such as the 'Universal Grammar' assumption, or in high-level legal arguments regarding 'presumption of innocence' (though 'suitei' is the specific term there, the concept of 'katei' is the root). You can effortlessly switch between 'Katei', 'Soutei', 'Suisoku', and 'Okusoku' to convey exact shades of meaning. For a C2 learner, 'Katei' is not just a word, but a fundamental building block of abstract thought and sophisticated discourse in Japanese.
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Entraîne-toi Exemples Notes et astuces

仮定 en 30 secondes

  • 仮定 (katei) means 'assumption' or 'hypothesis', used to set a logical premise.
  • It combines 'temporary' (仮) and 'fixed' (定) to create a provisional condition.
  • Commonly used in formal Japanese, business, science, and mathematics for 'if-then' logic.
  • Distinguished from 'yosou' (prediction) and 'kasetsu' (scientific hypothesis) by its logical function.

The Japanese word 仮定 (katei) is a cornerstone of logical reasoning, scientific inquiry, and everyday speculation. At its core, it represents the act of setting up a 'temporary' (仮) 'decision' or 'fixed state' (定). In linguistic and philosophical terms, it is the equivalent of an assumption or a hypothesis. Unlike a mere guess, a 仮定 serves as the foundation for a subsequent chain of thought. When you use this word, you are essentially saying, 'Let us treat this specific condition as true for a moment so we can see what follows.' This is vital in mathematics, law, and complex social planning where variables are numerous and outcomes are uncertain.

Etymology
The first kanji, 仮 (ka/kari), means temporary, provisional, or artificial. The second kanji, 定 (tei/sadameru), means to fix, determine, or establish. Together, they create the concept of a 'provisional establishment' of a fact.
Logical Function
In logic, it functions as the antecedent in an 'if-then' (if P, then Q) structure. Without the ability to form a 仮定, human reasoning would be limited strictly to observable facts, preventing us from planning for the future or analyzing the past.

「もし明日、雨が降ると仮定しましょう。その場合、イベントはどうなりますか？」 (Let's assume it rains tomorrow. In that case, what happens to the event?)

— Example of a situational assumption

In a broader sense, 仮定 allows for empathy and perspective-taking. By 'assuming' someone else's position, we can navigate social complexities. However, it is important to distinguish this from fact. A common phrase in Japanese debate is 「それはあくまで仮定の話です」 (That is strictly a hypothetical discussion), used to remind participants that the premise has not been proven. This distinction is crucial in professional settings like medicine or engineering, where acting on an unverified 仮定 without testing could lead to catastrophic results.

「犯人がこの窓から逃げたと仮定すると、つじつまが合います。」 (Assuming the culprit escaped through this window, it makes sense.)

Furthermore, in Japanese grammar, the term 仮定形 (kateikei) refers to the conditional form of verbs (e.g., 食べれば, 行けば). This grammatical category directly stems from the concept of setting a condition. Understanding 仮定 is therefore not just about vocabulary, but about understanding the very structure of how Japanese speakers process conditional reality. It is a word that bridges the gap between the known and the possible, the real and the imagined, and the cause and the effect.

Using 仮定 (katei) effectively requires understanding its role as both a noun and a verb (when combined with suru). It is most frequently found in formal discussions, academic writing, and logical puzzles. In everyday conversation, it often appears in the phrase 「仮定の話」 (a hypothetical story/talk) to signal that the speaker is not talking about reality.

Verb Usage: 〜と仮定する
This is the standard way to say 'to assume that...'. It usually follows a sentence ending in a plain form + と. For example: 「地球が平らだと仮定する」 (Assume the Earth is flat).
Noun Usage: 仮定に基づき
Meaning 'based on an assumption'. This is common in reports and research papers. 「この計画は、予算が増えるという仮定に基づいています。」 (This plan is based on the assumption that the budget will increase.)

「仮定の上に仮定を重ねても、答えは出ない。」 (Stacking assumption upon assumption won't give you an answer.)

When you want to propose a scenario for the sake of argument, you might start with 「仮に (kari ni)...」 which is the adverbial form. While related, 仮定 is the formal noun for the concept itself. In business meetings, you might hear 「最悪のケースを仮定して対策を練りましょう」 (Let's assume the worst-case scenario and develop a plan). This demonstrates the word's utility in risk management and strategic thinking.

「彼の話はすべて仮定に基づいているので、信頼性に欠ける。」 (His story is all based on assumptions, so it lacks reliability.)

In scientific contexts, 仮定 is often the first step of the scientific method, leading to a kasetsu (hypothesis). While kasetsu is specifically for scientific testing, 仮定 is broader and can be used for any logical premise. If you are learning Japanese for business or higher education, mastering the collocations of 仮定—such as katei wo oku (to make an assumption) or katei wo oifuseru (to challenge an assumption)—will significantly elevate your communicative competence.

You will encounter 仮定 (katei) in a variety of professional and intellectual environments. It is not a word you would typically use while buying vegetables at a market, but it is ubiquitous in the following settings:

  • Mathematics and Science: Teachers and researchers use it constantly. 「nが整数であると仮定すると...」 (Assuming n is an integer...). It is the bedrock of proofs.
  • Legal and Judicial Contexts: Lawyers use hypotheticals to test the limits of a law or to build a defense. 「もし被告人が現場にいなかったと仮定すれば...」 (If we assume the defendant was not at the scene...).
  • Business Strategy: During brainstorming sessions. 「売上が20%落ちると仮定して、予算を組み直しましょう。」 (Assuming sales drop by 20%, let's reconfigure the budget.)
  • Detective Fiction/Anime: Characters like Conan or Kindaichi often use 仮定 to reconstruct crimes. 「犯人が内部の人間だと仮定しよう。」 (Let's assume the culprit is an insider.)

「それはあくまで仮定の話ですよね？」 (That's just a hypothetical story, right?)

In news broadcasts, especially when discussing economic forecasts or climate change models, announcers use 仮定 to explain the parameters of the data being presented. For example, 「現在のペースで温暖化が進むと仮定した場合...」 (In the case where we assume global warming continues at the current pace...). This usage highlights the word's role in conveying serious, data-driven possibilities.

「もし私が社長だったと仮定して、意見を言わせてください。」 (Assuming I were the president, let me give my opinion.)

Finally, in the world of IT and programming, 仮定 is used when discussing logic gates and conditional branches. While the code uses if, the documentation and the engineers discussing the logic will use 仮定 to describe the conditions being checked. It is a word of precision, used to define the boundaries of a logical universe.

While 仮定 (katei) is a straightforward concept, learners often trip up on its nuance compared to similar words or its grammatical placement. Here are the most common pitfalls:

Confusing with 'Yosou' (予想)
Yosou is a prediction of what you think will actually happen. 仮定 is a condition you set regardless of whether you think it will happen. Mistake: 「明日の天気を仮定する」 (Incorrect if you mean 'predicting the weather').
Confusing with 'Kasetsu' (仮説)
Kasetsu is a scientific hypothesis that needs to be proven. 仮定 is a broader logical assumption. You 'assume' (katei) something to build an argument; you 'propose' a hypothesis (kasetsu) to conduct an experiment.

❌ 「彼の仮定は当たった。」 (His assumption was right - sounds awkward if you mean prediction.)
✅ 「彼の予想は当たった。」 (His prediction was right.)

Another common error is the confusion between the homophones 仮定 (assumption) and 課程 (course/curriculum) or 過程 (process). All three are pronounced 'katei'. Context is key: if you are talking about school, it's likely curriculum; if you are talking about how something was made, it's process; if you are talking about 'if', it's assumption.

❌ 「実験の仮定を説明する。」 (Explaining the assumption of the experiment - unless you mean the premise.)
✅ 「実験の過程を説明する。」 (Explaining the process of the experiment.)

Finally, learners sometimes forget to use the particle と when using the verb form. It should be 「AをBと仮定する」 (Assume A is B). Omitting the 'to' makes the sentence grammatically incomplete. Also, remember that 仮定 is quite formal. In casual speech with friends, using 「〜としたら」 or 「〜と考えてみて」 is much more natural than the stiff 仮定する.

Understanding 仮定 (katei) is easier when you see it in the context of its synonyms and related terms. Each has a specific 'flavor' of uncertainty.

仮説 (Kasetsu) - Hypothesis
Specifically used in science and research. It is an assumption that is intended to be tested and potentially proven true or false. 仮定 is the broader act of assuming.
推測 (Suisoku) - Guess/Inference
Making a judgment based on some evidence. Unlike 仮定, where you just 'set' a condition, suisoku involves trying to figure out the actual truth from clues.
想定 (Soutei) - Envisioning/Supposition
Often used in business and disaster prevention. It means 'imagining a likely scenario' to prepare for it. It is more practical and less abstract than 仮定.

「それは単なる推測に過ぎない。」 (That is nothing more than a guess.) vs. 「それを仮定として議論を進めよう。」 (Let's proceed with the discussion using that as an assumption.)

There is also 憶測 (okusoku), which means 'speculation' or 'conjecture', often with a negative nuance of having little to no evidence. While a 仮定 is a neutral tool for logic, an okusoku is often seen as gossip or groundless claims. In legal settings, you might hear 推定 (suitei), which means 'presumption' (e.g., 'presumed innocent' is muzai suitei). This is a legal 'assumption' that holds until proven otherwise.

「地震の規模をマグニチュード8と想定する。」 (Envisioning/supposing an earthquake of magnitude 8 for planning purposes.)

Finally, もしも (moshimo) is the most common casual equivalent. While 仮定 is the noun 'assumption', moshimo is the adverb 'if'. If you are writing a thesis, use 仮定. If you are writing a song about 'what if we never met', use moshimo. Understanding these distinctions allows you to choose the right level of formality and precision for any situation.

How Formal Is It?

Niveau de difficulté

Grammaire à connaître

仮定形 (Kateikei)

〜とすれば (If we assume)

〜としたら (If it were the case)

〜なら (If)

〜ば (Conditional)

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Exemples par niveau

1

もし、明日が休みだと仮定します。

Let's assume tomorrow is a holiday.

Uses 'to katei shimasu' to set a simple condition.

2

りんごが５個あると仮定しましょう。

Let's assume there are five apples.

A common way to start a simple math problem.

3

仮定の話をしましょう。

Let's talk about a hypothetical story.

'Katei no hanashi' is a set phrase.

4

ここが家だと仮定して遊ぼう。

Let's play assuming this is our house.

Using 'shite' to connect the assumption to an action.

5

もし、お金がたくさんあると仮定したら？

What if we assume we have a lot of money?

Combines 'moshi' and 'katei' for emphasis.

6

これは仮定です。

This is an assumption.

Simple A is B structure.

7

仮定の意味を教えてください。

Please tell me the meaning of 'assumption'.

Asking for a definition.

8

名前を「A」と仮定します。

Let's assume the name is 'A'.

Common in logic or coding examples.

1

新しい先生が来ると仮定して準備する。

Prepare assuming a new teacher is coming.

Connecting an assumption to a preparation verb.

2

仮定の質問に答えてください。

Please answer the hypothetical question.

'Katei no shitsumon' (hypothetical question).

3

彼が犯人だと仮定するのは早いです。

It's too early to assume he is the culprit.

Using 'no wa' to make the assumption the subject.

4

予算が足りないと仮定しましょう。

Let's assume the budget is not enough.

Setting a negative condition.

5

仮定に基づいた計画を立てる。

Make a plan based on an assumption.

'~ni motozuita' (based on).

6

それはただの仮定に過ぎません。

That is nothing more than an assumption.

'~ni sugimasen' (nothing more than).

7

もし雨が降ると仮定すれば、傘が必要です。

If we assume it will rain, we need umbrellas.

Using 'sureba' (if we do) with 'katei'.

8

仮定を一つずつ確認しましょう。

Let's check the assumptions one by one.

Treating 'katei' as a countable noun.

1

この理論は、ある仮定の上に成り立っている。

This theory is built upon a certain assumption.

'~no ue ni naritatsu' (to be built upon).

2

仮定の話ですが、もし宝くじが当たったらどうしますか？

This is a hypothetical, but what would you do if you won the lottery?

Using 'katei no hanashi desu ga' as a conversational softener.

3

まず、xを正の整数と仮定します。

First, assume x is a positive integer.

Standard academic phrasing.

4

その仮定が間違っていたら、どうなるのですか？

What happens if that assumption is wrong?

Questioning the validity of a premise.

5

条件を仮定することで、問題を単純化できる。

By assuming conditions, we can simplify the problem.

Using 'koto de' to show means/method.

6

仮定法は英語の文法で難しい部分だ。

The subjunctive mood is a difficult part of English grammar.

'Kateihou' is the grammatical term for subjunctive/conditional.

7

今の状況を最悪だと仮定して動こう。

Let's act assuming the current situation is the worst.

Setting a specific state ('worst') as the assumption.

8

あなたの仮定には証拠がありません。

There is no evidence for your assumption.

Critiquing an assumption.

1

科学的な議論には、明確な仮定が必要不可欠だ。

Clear assumptions are indispensable for scientific discussion.

'Hitsuyou fukaketsu' (indispensable).

2

仮定を置かずに結論を出すことはできない。

You cannot reach a conclusion without making assumptions.

'Katei wo oku' (to make/set an assumption).

3

そのモデルは、市場が安定しているという仮定に基づいている。

The model is based on the assumption that the market is stable.

Appositive clause: 'shijou ga antei shite iru to iu katei'.

4

仮定を現実と混同してはいけない。

One must not confuse assumptions with reality.

'A to B wo kondou suru' (to confuse A with B).

5

仮定を修正することで、より正確な予測が可能になる。

By revising the assumptions, more accurate predictions become possible.

'Katei wo shuusei suru' (to revise an assumption).

6

彼は仮定の話ばかりして、現実を見ようとしない。

He only talks about hypotheticals and won't look at reality.

'~bakari shite' (doing nothing but).

7

もし彼が嘘をついていると仮定すれば、全ての説明がつく。

If we assume he is lying, everything is explained.

'Setsumei ga tsuku' (to be explained/make sense).

8

不確定な要素を仮定として排除する。

Exclude uncertain elements as assumptions.

Using 'toshite' to define the role of the assumption.

1

この論文の妥当性は、初期の仮定に大きく依存している。

The validity of this paper depends heavily on the initial assumptions.

'Datousei' (validity) and 'izon suru' (depend on).

2

仮定を疑うことから、新しい発見が生まれる。

New discoveries are born from questioning assumptions.

Using 'koto kara' to show the source/origin.

3

非現実的な仮定を設けることは、思考実験において有効だ。

Setting unrealistic assumptions is effective in thought experiments.

'Shikou jikken' (thought experiment).

4

仮定が崩れれば、議論全体が瓦解する恐れがある。

If the assumptions collapse, the entire argument risks crumbling.

'Gakai suru' (to collapse/crumble).

5

暗黙の仮定を言語化し、共有することが重要だ。

It is important to verbalize and share implicit assumptions.

'Anmoku no katei' (implicit assumption).

6

その政策は、楽観的な仮定に立脚していると言わざるを得ない。

I must say that the policy is based on optimistic assumptions.

'Rikkyaku suru' (to be based on/grounded in).

7

仮定の枠組みを超えて考える必要がある。

It is necessary to think beyond the framework of assumptions.

'Wakugumi' (framework).

8

統計学において、帰無仮説は一種の仮定である。

In statistics, the null hypothesis is a type of assumption.

'Kimu kasetsu' (null hypothesis).

1

デカルトは、自らの存在以外のすべてを疑うという仮定から出発した。

Descartes started from the assumption of doubting everything except his own existence.

Historical/Philosophical context.

2

言語の普遍性を仮定するチョムスキーの理論は、言語学に革命をもたらした。

Chomsky's theory, which assumes the universality of language, revolutionized linguistics.

Complex appositive structure.

3

仮定の恣意性を排除することは、客観的な研究において極めて困難である。

Eliminating the arbitrariness of assumptions is extremely difficult in objective research.

'Shiisei' (arbitrariness).

4

我々の認識は、常に何らかの文化的仮定に規定されている。

Our perception is always prescribed by some kind of cultural assumption.

'Kitei sareru' (to be prescribed/stipulated).

5

仮定の連鎖を辿ることで、論理の脆弱性を浮き彫りにする。

By tracing the chain of assumptions, the vulnerability of the logic is highlighted.

'Ukibori ni suru' (to highlight/bring into relief).

6

数学的帰納法は、nの場合の成立を仮定し、n+1を証明する手法である。

Mathematical induction is a method that assumes the case for n and proves it for n+1.

Technical mathematical definition.

7

仮定を絶対視する教条主義は、知的進歩を阻害する。

Dogmatism, which treats assumptions as absolute, hinders intellectual progress.

'Zettaishi suru' (to treat as absolute).

8

存在論的な仮定を抜きにして、この哲学を語ることはできない。

One cannot discuss this philosophy without ontological assumptions.

'Sonzairontaki' (ontological).

Collocations courantes

仮定を置く (set an assumption)
仮定に基づく (based on an assumption)
仮定する (to assume)
仮定の話 (hypothetical talk)
仮定が崩れる (assumption collapses)
仮定を疑う (doubt an assumption)
仮定を修正する (revise an assumption)
暗黙の仮定 (implicit assumption)
非現実的な仮定 (unrealistic assumption)
仮定を設ける (establish an assumption)

Phrases Courantes

仮定の話ですが (This is a hypothetical, but...)
あくまで仮定です (It's strictly an assumption)
仮定の上に成り立つ (Built upon an assumption)
仮定法過去 (Past subjunctive)
仮定の域を出ない (Doesn't go beyond the realm of assumption)
仮定を前提とする (Take an assumption as a premise)
仮定を立てる (To make an assumption)
仮定を検証する (To verify an assumption)
仮定を認める (To accept an assumption)
仮定を覆す (To overturn an assumption)

Souvent confondu avec

仮定 vs 過程

仮定 vs 課程

仮定 vs 仮説

Expressions idiomatiques

"仮定の話には乗らない (I won't bite on a hypothetical)"
"仮定に仮定を重ねる (Stacking assumptions upon assumptions)"
"仮定の城 (A castle of assumptions - something fragile)"
"仮定を真実と履き違える (Mistaking an assumption for truth)"
"仮定の糸を辿る (Tracing the thread of an assumption)"
"仮定の海に溺れる (Drowning in assumptions/overthinking)"
"仮定の壁 (The wall of assumptions)"
"仮定を盾にする (Using an assumption as a shield/excuse)"
"仮定の翼を広げる (Spreading the wings of hypothesis/imagination)"
"仮定の迷宮 (A labyrinth of assumptions)"

Facile à confondre

仮定 vs 推定

仮定 vs 想定

仮定 vs 予想

仮定 vs 推測

仮定 vs 憶測

Structures de phrases

Famille de mots

Apparenté

仮説 (Hypothesis)
仮病 (Feigned illness)
仮名 (Kana/Pseudonym)
仮定形 (Conditional form)
仮定的 (Hypothetical)
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Comment l'utiliser

nuance

Katei is logical/abstract; Soutei is practical/situational.

formality

Highly formal, common in writing and speeches.

Erreurs courantes
  • Using 'Katei' for weather predictions.

    You don't 'assume' the weather for logic; you 'predict' it based on data.

  • Confusing 'Katei' (assumption) with 'Katei' (process).

    Process is about steps; assumption is about 'if'.

  • Forgetting the 'to' particle in 'A to katei suru'.

    The 'to' acts as a quotation mark for the assumption content.

  • Using 'Katei' in very casual settings.

    'Katei' is a stiff, academic word that can sound weird at a party.

  • Confusing 'Katei' with 'Kasetsu'.

    Kasetsu is for testing; Katei is for logical premises.

Astuces

Academic Writing

In research papers, always define your 'Katei' clearly in the introduction. This sets the boundaries for your logic. It prevents readers from criticizing you for things outside your scope. Use '〜と仮定する' to be explicit.

Softening Opinions

If you have a controversial opinion, frame it as a 'Katei'. Say 'Katei no hanashi desu ga...' (This is just a hypothetical...). This makes you sound less aggressive. It invites others to discuss the logic rather than the person.

Spotting Logic

When listening to a debate, listen for the word 'Katei'. It usually marks the starting point of an argument. If you can find a flaw in the 'Katei', the whole argument falls apart. It is the 'weak point' of any logical structure.

Kanji Breakdown

The 'Ka' (仮) radical on the left is 'person' (亻). A person wearing a mask is 'temporary' or 'fake'. The 'Tei' (定) has a 'roof' (宀) and 'correct' (正). A house that is correctly built is 'fixed'. A 'temporary fix' is an assumption.

Conditional Forms

Remember that the '~ba' form is called 'Kateikei'. This is because it sets a condition. When you learn 'tabereba' (if I eat), you are learning the 'Assumption Form'. Connecting the grammar name to the vocabulary word helps both stick.

Homophone Check

There are four common 'Katei's: Assumption (仮定), Process (過程), Curriculum (課程), and Home (家庭). Make a mental map of these. Assumption = Logic. Process = Steps. Curriculum = School. Home = Family. Context is your best friend.

Risk Management

In Japanese business, 'Katei' is used to build 'Case Studies'. You assume different market conditions to see how the company would survive. It's a sign of a thorough professional to present multiple 'Katei' scenarios.

Detective Novels

If you like mystery novels (推理小説), you will see 'Katei' a lot. Detectives 'Katei' a motive or a method to see if it fits the evidence. It's a great way to see the word used in a thrilling context.

If-Then Thinking

Practice 'If-Then' thinking in Japanese. 'A to katei suru. Naraba (then) B da.' This is the basic structure of logic. Even if you don't use it every day, understanding this structure improves your overall Japanese comprehension.

Polite Speculation

Japanese people often use 'Katei' to avoid being too direct. Instead of saying 'You are wrong', they might say 'If we assume your idea is true, then this problem happens...'. It's a way to be critical while remaining polite.

Mémorise-le

Origine du mot

Sino-Japanese (Kango).

Contexte culturel

Used to explore romantic or social 'what-ifs' in media.

Used to discuss risks without sounding pessimistic.

Central to math and science pedagogy.

Pratique dans la vie réelle

Contextes réels

Amorces de conversation

"もし明日、世界が終わると仮定したら何をしますか？"

"予算が無限にあると仮定して、旅行の計画を立てましょう。"

"彼が正しいと仮定すると、この問題はどう解決しますか？"

"仮定の話ですが、もし魔法が使えたらどうしますか？"

"今の仕事がなくなると仮定して、将来を考えてみませんか？"

Sujets d'écriture

自分の人生が映画だと仮定して、今の章にタイトルをつけてください。

もし10年前に戻れると仮定したら、何を変えますか？

「成功は約束されている」という仮定で、新しい挑戦を書いてください。

社会のルールが一つ消えると仮定して、その影響を考察してください。

自分が他人の心を読むことができると仮定して、そのメリットとデメリットを書いてください。

Questions fréquentes

10 questions

Katei is a general assumption used in logic. Kasetsu is a specific hypothesis used in science that requires testing. You assume (katei) something to build a theory, but you propose a hypothesis (kasetsu) to prove it. In daily life, Katei is more common for 'what-ifs'. Kasetsu sounds like you are a researcher.

Yes, but usually in the phrase 'Katei no hanashi' (a hypothetical talk). Using 'Katei suru' in a casual chat might sound a bit stiff or overly logical. For simple 'if' scenarios with friends, stick to 'moshi' or '~tara'. Use 'Katei' when you want to emphasize the logical nature of the scenario.

Context is everything. If the topic is logic, math, or 'if', it's 仮定 (assumption). If the topic is 'how something happened' or 'steps', it's 過程 (process). If the topic is school subjects or a degree, it's 課程 (curriculum). Listen for verbs like 'motozuku' (based on) for assumption and 'susumu' (proceed) for process.

Kateihou (仮定法) is a grammatical term meaning 'subjunctive mood' or 'conditional mood'. It refers to the rules for making 'if' sentences. 'Katei' is the noun meaning the 'assumption' itself. So, you use the 'Kateihou' grammar to express a 'Katei'.

The most common particle is 'to'. You say '[Sentence/Noun] + to katei suru'. You can also use 'wo' if you are treating the assumption as a direct object, like 'Katei wo oku' (to set an assumption). 'To' is used for the content of the assumption.

Yes! 'Kari ni' (仮に) is an adverb that means 'supposing' or 'for the sake of argument'. It uses the same first kanji (仮). You often use them together: 'Kari ni A da to katei shimashou' (Supposingly, let's assume it is A).

It means 'implicit assumption' or 'hidden assumption'. These are things people assume to be true without saying them out loud. In a debate, identifying someone's 'anmoku no katei' is a powerful way to challenge their logic. It's a very common phrase in academic writing.

No, that is 'Katei' (家庭). It is pronounced the same but uses different kanji: 家 (house) and 庭 (garden). This is another common homophone to be careful with! 'Assumption' uses 'Temporary' and 'Fixed'.

Use 'Soutei' (想定) when you are preparing for a specific scenario, like a disaster or a business risk. 'Katei' is for abstract logic. If you are saying 'Let's prepare for a flood', use Soutei. If you are saying 'If x equals 2', use Katei.

Not necessarily. A 'Katei' is something you *treat* as true for a moment, regardless of its actual state. It could be true, or it could be false. The point is to see what the logical result would be if it *were* true.

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