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B2 noun 8 min de leitura

一因

ichiin

Pratique Exemplos Notas e dicas 一因 em 30 segundos

Explicação 一因 in your Level:

At the A1 level, you don't need to use '一因' (ichiin) yet. It is too formal. Instead, you learn '理由' (riyuu), which means 'reason.' For example, '理由は何ですか？' (What is the reason?). '一因' is like saying 'one reason' but in a very serious way. Imagine you have a big pizza called 'The Reason.' '一因' is just one slice of that pizza. At this level, just remember that Japanese has special words for talking about parts of a reason when things are complicated. You will mostly see '一' (one) and '因' (cause) separately in other words before you use them together like this.

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At the A2 level, you might start seeing '一因' (ichiin) in simple news stories or textbooks. It means 'one cause.' You know the word '原因' (gen'in) for 'cause.' '一因' is just a more specific version that says 'this is one cause, but there are others.' For example, if you say 'Lateness is one cause of bad grades,' you use '一因.' It's a useful word because it shows you know that life is not simple. It's usually used with 'です' (desu). Example: 'ストレスが病気の一因です' (Stress is one cause of illness). This sounds much more 'grown-up' than just saying 'Stress is the reason.'

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At the B1 level, you should begin to recognize '一因' (ichiin) in reading passages, especially those about social issues or health. This word is a 'noun' that acts as a 'contributing factor.' You will often see it in the pattern '[Noun] は [Noun] の一因だ'. It is common in the JLPT N3 level. Using '一因' helps you avoid sounding like you are blaming only one thing for a big problem. For instance, instead of saying 'The rain caused the accident,' you could say 'The rain was ONE cause of the accident' (雨が事故の一因だった), which implies the driver might have also been tired or the car was old. It is a very polite and objective way to speak.

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At the B2 level, '一因' (ichiin) is a core part of your vocabulary for academic writing and professional discussion. You should use it to show nuance. It is often paired with verbs like 'となる' (to become) or 'と考えられている' (is thought to be). At this level, you distinguish between '原因' (the overall cause), '主因' (the main cause), and '一因' (one of several causes). You will encounter it in complex texts discussing economics, environmental science, and sociology. Mastering this word allows you to participate in 'multi-factorial analysis'—the ability to discuss how many different things work together to create a result. It is a key word for JLPT N2.

At the C1 level, you use '一因' (ichiin) to structure complex arguments. You might use it to introduce a minor but significant factor before moving on to more critical ones. It is often used in the phrase '一因を担う' (to play a part in/to be a factor in). You understand the subtle difference between '一因' and '要因' (yōin), where '一因' is more singular and '要因' is more categorical. In a C1 level essay, you might write: '政策の失敗が、現在の経済停滞を招いた一因であることは否定できない' (It cannot be denied that policy failures are one factor that led to the current economic stagnation). It provides a level of academic rigor to your Japanese.

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At the C2 level, '一因' (ichiin) is used with precision in high-level discourse, legal documents, and scientific journals. You recognize its use in 'causal attribution' and how it functions to limit liability or scope in professional reporting. You can use it in sophisticated structures like '一因に帰せられる' (can be attributed as one cause). You also understand how the word functions within the broader context of Japanese 'aimai' (ambiguity) culture, where identifying something as 'one cause' rather than 'the cause' can be a strategic move to avoid direct confrontation or overstatement. Your usage is indistinguishable from a highly educated native speaker, using it to balance complex multi-variable explanations perfectly.

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Pratique Exemplos Notas e dicas

一因 em 30 segundos

Ichiin means 'one cause' out of many. It is a formal word used for analysis.
Use it to show that a situation is complex and has multiple reasons.
It is common in news, business reports, and academic writing (JLPT N2 level).
Typical patterns include 'X is one cause of Y' or 'X became a cause of Y'.

The Japanese noun 一因 (ichiin) is a sophisticated way to identify a single contributing factor within a complex web of reasons. In English, we often translate this as 'one of the causes,' 'a contributing factor,' or 'one reason.' The beauty of this word lies in its humility and accuracy; by using it, you are explicitly acknowledging that the situation you are describing is not simple and that other factors are also at play. It prevents the speaker from sounding overly simplistic or reductive.

Etymology and Nuance: The word is composed of 一 (ichi) meaning 'one' and 因 (in) meaning 'cause' or 'factor.' Unlike the word 原因 (gen'in), which often points to the primary or sole cause of an event, 一因 suggests that the speaker has analyzed the situation and identified this specific element as part of the whole. It is frequently used in academic writing, news reports, and professional post-mortems where multiple variables must be considered.
Contextual Application: You will encounter this word most often when discussing social issues, economic trends, or health matters. For instance, if a company's profits drop, a manager might say that the rising cost of raw materials is 一因, implying that marketing failures or competition are also factors. In medicine, a doctor might say that lack of sleep is 一因 for a patient's high blood pressure, acknowledging genetics and diet as well.

地球温暖化が、近年の異常気象の一因であることは疑いようがない。
— Global warming is undoubtedly one of the causes of recent extreme weather.

In terms of grammar, it is almost always used as a noun, often followed by the copula だ (da), です (desu), or である (de aru). It can also modify other nouns using the particle の (no). For example, 一因としての不況 (recession as one of the causes). It is rarely used in very casual speech; instead, you might hear 理由の一つ (riyuu no hitotsu) in everyday conversation. However, mastering 一因 will significantly elevate your Japanese proficiency level to B2 and beyond, allowing you to participate in more formal and intellectual discussions.

彼の不注意が事故の一因となった。
— His carelessness became one of the causes of the accident.

Comparison with Similar Terms: While 要因 (yōin) also means 'factor,' it tends to refer to more abstract or structural elements. 一因 is more concrete and specifically emphasizes that it is just *one* piece of the puzzle. If you want to say 'The primary cause,' you would use 主因 (shuin) or 最大の原因 (saidai no gen'in). If you want to say 'The root cause,' use 根本的な原因 (konpon-teki na gen'in).

Using 一因 correctly requires understanding its typical sentence structures. It usually acts as the predicate of a sentence or as a noun phrase identifying a factor. The most common pattern is: [Factor] は [Result] の一因だ (Factor is one cause of Result).

Pattern 1: Identification (X is one cause of Y): This is the most straightforward usage. You state a fact and categorize it as one of several causes.

ストレスは、現代社会における病気の大きな一因です。 (Stress is a major contributing factor to illness in modern society.)
Pattern 2: Becoming a Cause (X became one cause of Y): Using the verb となる (to naru), you can describe how an event or condition turned into a contributing factor.

少子高齢化が、労働力不足の一因となっている。 (The declining birthrate and aging population are becoming one cause of the labor shortage.)

不十分な睡眠は、集中力低下の一因となります。
— Insufficient sleep becomes one cause of decreased concentration.

You can also use 一因 to qualify a statement when you don't want to blame a single thing entirely. This is very common in corporate reports or academic papers where 'proof' of a single cause is difficult to establish. It shows a nuanced understanding of causality.

円安が、輸入食品の価格高騰の一因だと考えられている。
— The weak yen is thought to be one cause of the soaring prices of imported food.

Pattern 3: Attributing Success or Failure: It is not always negative. You can use it to describe one of the reasons for success.

チームの結束力が、今回の優勝の一因だ。 (The team's unity is one of the reasons for this victory.)

If you turn on the NHK news or read an editorial in the Asahi Shimbun, you will hear 一因 almost daily. It is the language of analysis. Here are the specific environments where this word thrives:

1. News and Journalism: Reporters use it to explain complex events like stock market crashes, political scandals, or natural disasters. It sounds more professional than '理由' (riyuu).

「今回の選挙の敗北は、若者の政治離れが一因とされています。」 (This election defeat is said to be caused in part by the political apathy of young people.)
2. Academic Lectures and Research: In university settings, professors use it when discussing historical events or scientific phenomena where multiple variables are involved. It is an essential word for JLPT N2 and N1 reading passages.

「原材料費の変動が、収益悪化の一因です」と社長は述べた。
— "Fluctuations in raw material costs are one cause of the decline in profits," the president stated.

In business meetings, using 一因 shows that you have a broad view of the situation. If you are asked why a project is delayed, saying 'I am the reason' (私のせいです) is too personal and dramatic. Saying 'A delay in shipping was one cause' (配送の遅れが一因です) sounds like a professional analysis of the logistics chain.

SNSの普及が、情報の拡散スピードを速めた一因だ。
— The spread of SNS is one factor that accelerated the speed of information dissemination.

3. Medical Consultations: Doctors use it to discuss lifestyle diseases. '運動不足が糖尿病の一因です' (Lack of exercise is one cause of diabetes). It frames the cause as a contributing factor rather than a definitive, sole trigger.

Even advanced learners sometimes misuse 一因. The most frequent errors involve confusing it with its synonyms or using it in contexts that are too simple.

1. Confusing '一因' (Ichiin) with '原因' (Gen'in): This is the biggest pitfall. 原因 is the general word for 'cause.' If there is only one clear cause (e.g., the light is off because the bulb is broken), using 一因 sounds strange. It implies there are other reasons the light might be off, which in that case, there aren't.
2. Using it in Casual Conversation: If you're talking to a friend about why you were late for lunch, saying '渋滞が一因です' (Traffic was one cause) sounds incredibly stiff and robotic. Instead, say '渋滞してたから' or '理由の一つは渋滞だよ'. Save 一因 for writing, speeches, or professional settings.

❌ 鍵を忘れたのが、家に入れない一因だ。
✅ 鍵を忘れたのが、家に入れない原因だ。
— Explanation: Forgetting the key is the *only* reason you can't enter. Using '一因' suggests there are other reasons, which is confusing.

3. Overusing '一因' for Positive Results: While technically possible, 一因 is more frequently used for negative or neutral analysis. For positive outcomes, words like 勝因 (shōin - cause of victory) or 要因 (yōin - factor) are often preferred. For example, '成功の要因' sounds more natural than '成功の一因', although the latter is not grammatically wrong.

To truly master 一因, you must know how it fits into the hierarchy of Japanese words for 'cause' and 'reason.' Here is a comparison with its closest relatives.

原因 (Gen'in) vs. 一因 (Ichiin): 原因: General term for cause. Can be the sole cause or the main cause.
一因: Specifically 'one of many causes.' Much more formal and analytical.
要因 (Yōin) vs. 一因 (Ichiin): 要因: An important factor or primary element. Often used for structural or background factors (e.g., 'Economic factors').
一因: A single cause. It is more specific and singular than 要因. You can have multiple 要因, but 一因 points to just one from the group.

不況は、倒産の一因にすぎない。
— The recession is merely one cause of the bankruptcy. (Implies other factors like bad management were also involved).

理由 (Riyū) vs. 一因 (Ichiin): 理由: The broad word for 'reason.' Used in daily life, for personal motivations, or logical explanations.
一因: Used for objective analysis of events. You wouldn't say 'The reason I like cats is 一因'.
契機 (Keiki) / きっかけ (Kikkake): These mean 'trigger' or 'catalyst.' While 一因 is a contributing factor, きっかけ is the specific spark that set things in motion.

How Formal Is It?

Curiosidade

While '因' on its own is ancient, the specific compound '一因' became highly popular in the Meiji era as Japan adopted Western scientific and logical methods of analysis, requiring more specific words for causality.

Guia de pronúncia

UK i.tɕi.iɴ

US i.tʃi.in

Heiban (Flat) pitch accent: いちいん [0].

Rima com

じいん (jiin - temple) きいん (kiin - cause/origin) しんいん (shin'in - true cause) りいん (riin - official) いいん (iin - committee member) しん (shin - heart) びん (bin - bottle) きん (kin - gold)

Erros comuns

Pronouncing it like 'ichin' (skipping the second 'i').
Over-stressing the 'n' sound like an English 'n'.
Mixing it up with 'ichi-ban' (number one).
Confusing the pitch with 'ichi' (one) which can have a different accent.
Pronouncing 'chi' as 'shi'.

Nível de dificuldade

Leitura 4/5

The kanji are simple, but the word appears in complex contexts.

Escrita 5/5

Requires understanding of formal sentence structures.

Expressão oral 4/5

Hard to use naturally without sounding overly stiff.

Audição 3/5

Easy to recognize once you know the 'ichi' + 'in' combination.

O que aprender depois

Pré-requisitos

原因 (gen'in) 理由 (riyuu) 一つ (hitotsu) 因る (yoru) 結果 (kekka)

Aprenda a seguir

要因 (yōin) 主因 (shuin) 敗因 (haiin) 勝因 (shōin) 素因 (soin)

Avançado

帰属理論 (attribution theory) 因果関係 (causal relationship) 多角的 (multi-faceted) 連鎖 (chain/sequence) 特定 (specification)

Gramática essencial

Noun + の一因だ

不注意が事故の一因だ。

Noun + が一因となる

不況が失業の一因となる。

Noun + を一因として

不祥事を一因として、社長が辞任した。

Noun + も一因である

性格の不一致も離婚の一因である。

一因にすぎない

それは失敗のほんの一因にすぎない。

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Exemplos por nível

これは失敗の理由の一つです。

This is one of the reasons for the failure.

A1 level uses '理由の一つ' instead of '一因'.

一つの原因は雨です。

One cause is the rain.

Simple '一つ' + '原因'.

食べすぎは太る理由です。

Eating too much is a reason for getting fat.

Basic 'A is B' structure.

一因という言葉は難しいです。

The word 'ichiin' is difficult.

Using the word as a subject.

不注意が事故の元です。

Carelessness is the source of accidents.

'元' (moto) is often used for 'cause' in A1/A2.

風が強いのが理由です。

The strong wind is the reason.

Nominalizing the clause with 'のが'.

練習不足が一因かもしれません。

Lack of practice might be one cause.

Introduction of '一因' with 'かもしれない'.

これがその一因です。

This is one of the causes.

Simple demonstrative use.

不況がその一因だと言われています。

It is said that the recession is one cause.

Passive form 'と言われている'.

野菜不足が病気の一因になります。

Lack of vegetables becomes one cause of illness.

Verb 'になる' (to become).

彼のミスも一因でした。

His mistake was also one factor.

Particle 'も' shows there are other factors.

円安が値上げの一因です。

The weak yen is one cause of the price hike.

Noun + の + 一因.

これが問題の大きな一因です。

This is a major cause of the problem.

Adjective '大きな' modifying '一因'.

寝不足がミスの一因になりました。

Lack of sleep became one cause of the mistake.

Past tense 'になりました'.

準備不足が負けた一因です。

Lack of preparation is one reason for the loss.

Clause modifying '一因'.

一因を調べる必要があります。

It is necessary to investigate the cause.

Verb '調べる' (investigate).

地球温暖化が異常気象の一因となっている。

Global warming is becoming one cause of extreme weather.

Continuative form 'となっている'.

少子化は、将来の労働力不足の一因だ。

The declining birthrate is one cause of future labor shortages.

Noun modification with 'の'.

ストレスが現代病の一因と考えられている。

Stress is thought to be one cause of modern diseases.

Passive structure 'と考えられている'.

交通渋滞が遅刻の主な一因でした。

Traffic congestion was a major contributing factor to the lateness.

Adjective '主な' (main/major).

不規則な生活が体調不良の一因になる。

An irregular lifestyle becomes one cause of poor health.

General truth expressed with 'になる'.

情報の不足が混乱の一因となった。

The lack of information became a factor in the confusion.

Past tense 'となった'.

この古い設備が事故の一因かもしれない。

This old equipment might be one cause of the accident.

Conjecture with 'かもしれない'.

一因を特定するのは難しい。

Identifying a single cause is difficult.

Nominalized verb phrase '特定するのは'.

過度な競争が、若者の精神的疲労の一因と指摘されている。

Excessive competition is pointed out as one cause of mental fatigue among youth.

Formal passive 'と指摘されている'.

海外市場の変動が、収益減少の一因となったことは明らかだ。

It is clear that fluctuations in overseas markets were one cause of the decline in profits.

Formal structure '...ことは明らかだ'.

都市部への人口集中が、地方衰退の一因となっている。

The concentration of population in urban areas is a factor in the decline of rural areas.

Noun phrase '人口集中' as the subject.

食生活の変化が、生活習慣病の増加の一因である。

Changes in dietary habits are one cause of the increase in lifestyle-related diseases.

Formal copula 'である'.

コミュニケーション不足が、プロジェクト失敗の一因として挙げられた。

Lack of communication was cited as one factor in the project's failure.

'一因として' (as a cause).

技術革新が、産業構造の変化の一因を担っている。

Technological innovation plays a part in the change of industrial structure.

Idiomatic '一因を担っている' (plays a part).

不十分な教育が、貧困の連鎖の一因となり得る。

Inadequate education can become a factor in the cycle of poverty.

Potential form 'となり得る' (can become).

複数の要因が絡み合っているが、これも一因に違いない。

Multiple factors are intertwined, but this is undoubtedly one of them.

Strong conviction 'に違いない'.

マクロ経済の不安定さが、投資意欲減退の一因を構成している。

Macroeconomic instability constitutes one of the factors behind the decline in investment appetite.

Academic verb '構成している' (constitutes).

歴史的背景の複雑さが、現在の紛争の一因であることを忘れてはならない。

We must not forget that the complexity of the historical background is one cause of the current conflict.

Formal imperative '忘れてはならない'.

格差の拡大が、社会不安を増大させる一因として作用している。

The widening gap is acting as a factor that increases social unrest.

Functional verb '作用している' (acting as).

当該企業の不透明な会計処理が、株価暴落の一因と目されている。

The company's opaque accounting practices are seen as a factor in the stock price crash.

Formal passive 'と目されている' (seen as/regarded as).

言語の壁が、異文化理解を妨げる一因であることは自明の理だ。

It is a self-evident truth that the language barrier is one factor hindering cross-cultural understanding.

Advanced idiom '自明の理' (self-evident truth).

資源の枯渇が、将来的な地政学的リスクの一因を形成するだろう。

The depletion of resources will likely form one of the causes of future geopolitical risks.

Analytical '一因を形成する'.

個人の意識の変化が、伝統文化の衰退の隠れた一因となっている。

Changes in individual consciousness are becoming a hidden cause of the decline of traditional culture.

Adjective '隠れた' (hidden).

一因を排除したところで、根本的な解決には至らない。

Even if we eliminate one cause, it will not lead to a fundamental solution.

Conditional 'したところで' (even if).

構造的な欠陥が、システムの脆弱性を露呈させる一因に帰せられる。

Structural defects can be attributed as a factor that exposed the system's vulnerability.

Formal 'に帰せられる' (be attributed to).

環境破壊が生物多様性の喪失に及ぼす影響は、多角的分析における一因に過ぎない。

The impact of environmental destruction on the loss of biodiversity is merely one factor in a multi-faceted analysis.

Limitative 'に過ぎない' (merely).

認識論的な差異が、両国間の交渉が決裂した深層的一因である。

Epistemological differences are a deep-seated factor in the breakdown of negotiations between the two countries.

Philosophical term '認識論的' (epistemological).

パラダイムシフトの遅れが、産業競争力低下の決定的一因となった。

The delay in the paradigm shift became a decisive factor in the decline of industrial competitiveness.

Strong adjective '決定的' (decisive).

グローバル化の進展が、地域コミュニティの解体の一因を担う側面は否めない。

It cannot be denied that the progress of globalization plays a part in the dismantling of local communities.

Complex double negative '否めない' (cannot be denied).

心理学的バイアスが、意思決定を誤らせる一因として介在している。

Psychological biases are intervening as a factor that leads to erroneous decision-making.

Academic verb '介在している' (intervening).

一因を究明することは、再発防止策を講じる上での必須条件である。

Investigating the cause is a prerequisite for taking measures to prevent recurrence.

Formal '講じる上での' (for the purpose of taking).

偶発的な事象が、歴史の転換点における一因を成す場合も少なくない。

It is not uncommon for accidental events to form a factor at historical turning points.

Formal '一因を成す' (to form a factor).

Sinônimos

要因原因要素きっかけ理由

Antônimos

結果結末全因

Colocações comuns

一因となる

大きな一因

一因を担う

一因として挙げられる

一因にすぎない

一因を特定する

一因を探る

一因を構成する

主な一因

隠れた一因

Frases Comuns

失敗の一因

— One of the reasons for failure. Used to analyze what went wrong.

準備不足が今回の失敗の一因だ。

成功の一因

— One of the reasons for success. Used to attribute credit.

幸運も成功の一因だったと言える。

事故の一因

— One cause of an accident. Used in police or safety reports.

スピード違反が事故の一因である。

不況の一因

— One cause of a recession. Common in economic news.

原油高が不況の一因となっている。

病気の一因

— One cause of illness. Common in medical advice.

偏食は多くの場合、病気の一因となる。

混乱の一因

— One cause of confusion. Used when many things are messy.

指示の遅れが現場の混乱の一因だ。

不振の一因

— One cause of a slump or poor performance.

主力の怪我がチーム不振の一因だ。

高騰の一因

— One cause of a price surge.

供給不足が野菜高騰の一因だ。

劣化の一因

— One cause of deterioration or worsening.

湿気が建物の劣化の一因となる。

誤解の一因

— One cause of a misunderstanding.

言葉の不足が誤解の一因となった。

Frequentemente confundido com

一因 vs 原因 (gen'in)

Gen'in is the general 'cause'. Ichiin is specifically 'ONE of the causes'.

一因 vs 要因 (yōin)

Yōin is a 'factor' (often structural). Ichiin is a single 'cause' (often an event or condition).

一因 vs 動機 (douki)

Douki is a 'motive' (psychological). Ichiin is a 'cause' (objective/factual).

Expressões idiomáticas

"一因を担う"

— To play a part in causing something; to bear some of the responsibility.

彼もこの問題の一因を担っている。

Formal

"一因に帰する"

— To attribute something to a single factor (among others).

失敗を不運の一因に帰する。

Academic

"一因を成す"

— To form or constitute one of the causes.

その出来事が歴史の転換点の一因を成した。

Formal/Literary

"一因を排除する"

— To eliminate one of the causes.

リスクの一因を排除する作業を行う。

Professional

"一因として作用する"

— To act as a contributing factor.

円高が輸出減少の一因として作用した。

Economic/Academic

"一因を究明する"

— To investigate and clarify one of the causes.

事故の隠れた一因を究明する。

Formal

"一因を突き止める"

— To track down or identify one of the causes.

故障の意外な一因を突き止めた。

Neutral/Formal

"一因を露呈する"

— To expose one of the underlying causes.

不祥事が組織の腐敗の一因を露呈した。

Formal

"一因に過ぎない"

— To be nothing more than one cause (downplaying importance).

それは膨大な問題のほんの一因に過ぎない。

Neutral/Formal

"一因を共有する"

— To share a common cause/factor with something else.

これら二つの現象は一因を共有している。

Academic

Fácil de confundir

一因 vs 起因

Both contain '因'.

起因 (kiin) is a verb/noun meaning 'to originate from' or 'the origin.' It focuses on the starting point.

不注意に起因する事故。

一因 vs 死因

Contains '因'.

死因 (shiin) is specifically the 'cause of death.' You cannot say '死の一因' as easily as '死因'.

彼の死因は心不全だった。

一因 vs 勝因

Focuses on success.

勝因 (shōin) is specifically the cause of 'victory.' Ichiin is more neutral.

チームワークが勝因だ。

一因 vs 敗因

Focuses on failure.

敗因 (haiin) is specifically the cause of 'defeat.'

油断が敗因となった。

一因 vs 素因

Academic/Medical context.

素因 (soin) refers to a 'predisposition' or a background factor that makes something likely to happen.

遺伝的素因が強い。

Padrões de frases

[A]は[B]の一因だ。

ストレスは病気の一因だ。

[A]が[B]の一因となっている。

円安が物価高の一因となっている。

[A]も[B]の一因と考えられる。

不注意も事故の一因と考えられる。

[A]が[B]の一因を担っている。

技術革新が成長の一因を担っている。

[A]は[B]の一因にすぎない。

それは問題のほんの一因にすぎない。

[A]を一因として[B]が引き起こされた。

震災を一因として経済危機が引き起こされた。

[A]が[B]の一因を成す。

その法改正が混乱の一因を成した。

[A]の大きな一因は[B]である。

失敗の大きな一因は準備不足である。

Família de palavras

Substantivos

要因 (yōin - factor)

主因 (shuin - main cause)

死因 (shiin - cause of death)

勝因 (shōin - cause of victory)

敗因 (haiin - cause of defeat)

Verbos

因る (yoru - to be caused by)

起因する (kiin suru - to originate from)

Relacionado

原因 (gen'in)

理由 (riyuu)

因果 (inga - cause and effect)

因縁 (innen - fate/connection)

素因 (soin)

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Como usar

frequency

Common in formal writing, news, and professional settings. Rare in daily spoken conversation.

Erros comuns

Using '一因' when there is only one cause. → Use '原因' or '理由'.
If the only reason you are wet is the rain, don't say rain is '一因'. It sounds like you're hiding something else.
Saying '一因をします' (doing a cause). → Use '一因となる' or '一因である'.
Ichiin is a noun that describes a state, not an action you perform.
Using it in very casual slang. → Use '理由の一つ'.
It sounds like you're reading a textbook while hanging out with friends.
Confusing '一因' (ichiin) with '委員' (iin - committee member). → Pay attention to the 'chi' sound.
The pronunciation is similar, but the meanings are completely different.
Forgetting the particle 'の' when connecting nouns. → 事故の一因 (Accident's one cause).
Japanese nouns need 'の' to link them in this context.

Dicas

Nuance Check

Always check if there are multiple reasons. If you can list at least two, '一因' is safe to use.

Essay Structure

In an essay, use 'まず、一因として...' (First, as one cause...) to introduce your first point professionally.

Particle Choice

Use 'が' for the subject causing the effect: '不注意が、事故の一因だ。'

News Keywords

When you hear '一因' on the news, the reporter is trying to be objective and avoid bias.

Kanji Meaning

Focus on the '因' (in) kanji. It appears in '原因', '要因', and '因果'. It always means 'cause'.

Business Etiquette

Use it to soften blame. 'My mistake was one cause' sounds better than 'I did it' in a formal report.

N2/N1 Prep

Look for '一因' in passages about the environment or population decline. It's a high-frequency word there.

Harmonious Speech

Remember that '一因' is part of the Japanese linguistic strategy of not being too direct or absolute.

The Pie Slice

Visualize a pie chart. '一因' is one slice. The whole pie is the '原因'.

Logic

If you say 'X is 一因', you are admitting you don't know the whole story, which is often very honest.

Memorize

Mnemônico

Think of 'Ichi' (One) and 'In' (Inside/Cause). It is 'One' factor 'In' the whole mess.

Associação visual

Imagine a pie chart where one slice is labeled '一因'. The whole pie is the '原因' (Cause), but you are pointing at just one piece.

Word Web

原因 (Root) 一因 (Branch) 要因 (Type) 主因 (Center) 敗因 (Failure) 勝因 (Success) 死因 (Death) 素因 (Base)

Desafio

Try to list three '一因' for why you are learning Japanese. (e.g., Anime is '一因', career is '一因', travel is '一因'.)

Origem da palavra

Borrowed from Middle Chinese roots. '一' (one) + '因' (cause/criterion).

Significado original: A single cause or a single factor.

Sino-Japanese (Kango).

Contexto cultural

Be careful when using '一因' regarding personal mistakes; it can sometimes sound like you are making excuses by spreading the blame.

English speakers often use 'one of the reasons' which is less formal than '一因'. 'Contributing factor' is the closest professional equivalent.

Used in NHK's 'Close-up Gendai' for social analysis. Common in the writings of Natsume Soseki when analyzing human nature. Frequent in government 'White Papers' (Hakusho) to explain societal trends.

Pratique na vida real

Contextos reais

Economics

円安が一因だ
不況の一因となる
市場の混乱の一因
格差拡大の一因

Medicine

生活習慣が一因
遺伝が一因かもしれない
ストレスが病気の一因
運動不足が一因だ

Accidents/Safety

整備不良が一因
人為的ミスが一因
天候が一因となった
一因を究明する

Education/Success

努力が成功の一因
指導不足が失敗の一因
環境が一因である
一因を分析する

Environment

排ガスが温暖化の一因
森林破壊が一因だ
異常気象の一因
一因として作用する

Iniciadores de conversa

"最近の物価高の一因は何だと思いますか？ (What do you think is one cause of the recent price hikes?)"

"あなたの成功の一因を教えてください。 (Please tell me one of the reasons for your success.)"

"不眠がストレスの一因になることはありますか？ (Can lack of sleep be a factor in stress?)"

"渋滞がこの街の遅刻の一因ですよね。 (Traffic is one cause of lateness in this city, isn't it?)"

"プロジェクトが遅れた一因は何でしょうか？ (What was one of the causes for the project delay?)"

Temas para diário

自分の人生が好転した一因について、具体的に書いてみましょう。 (Write specifically about one factor that caused your life to improve.)

最近の社会問題（例：孤独）の一因について分析してください。 (Analyze one cause of a recent social issue, e.g., loneliness.)

仕事や勉強でミスをした時、その一因は何だったか振り返ってください。 (When you made a mistake at work or study, reflect on what one of the causes was.)

健康を維持するための一因として、何を大切にしていますか？ (What do you value as one factor for maintaining health?)

新しい言語を学ぶことが、あなたの視野を広げる一因になっていますか？ (Is learning a new language a factor in broadening your perspective?)

Perguntas frequentes

10 perguntas

Yes, you can. For example, 'His hard work was one cause (一因) of the success.' However, '要因' or '勝因' are often more common for positive results.

Rarely. It sounds very formal. If you use it with friends, they might think you are speaking like a news reporter. Use '理由の一つ' instead.

'一因' (ichiin) means 'one cause,' while '要因' (yōin) means 'factor.' '要因' is often used for broad categories (economic factors), while '一因' is used for a specific reason.

No. '二因' is not a standard word. You would say '二つの要因' or '二つの原因'.

Yes, absolutely. That is the core meaning of the word. If there is only one cause, do not use '一因'.

Yes, it is commonly found in JLPT N2 and N1 reading and listening sections.

It is written as '一' (one) and '因' (cause/factor).

No, it is a noun. You must use it with a verb like 'となる' (to become) or 'である' (to be).

Yes. While '原因' is neutral and can be used anywhere, '一因' is specifically used for formal analysis.

There is no direct single-word opposite, but '主因' (main cause) or '結果' (result) are often used in contrast.

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