Quintuple VS
Synonym Boundary: "理由", "理性", "いわく", "所以", "国家理性"
All represent the core concept "reason", but require precise selection.
Japanese Option A
理由
りゆう (riyū)
N4 / CEFR
Japanese Option B
理性
りせい (risei)
N3 / CEFR
Japanese Option C
いわく
いわく (iwaku)
N2 / CEFR
Japanese Option D
所以
ゆえん (yuen)
N1 / CEFR
Japanese Option E
国家理性
こっかりせい (kokkarisei)
C2 / CEFR
Quintuple VS Nuance Contrast & Social Differences
When expressing "reason" in Japanese, you must carefully distinguish between "理由", "理性", "いわく", "所以", "国家理性" based on context.
- 理由 (りゆう (riyū) - Level: N4): Maps to "reason, motive" and is used when A noun referring to the cause or explanation for something. Often used with なぜ.
- 理性 (りせい (risei) - Level: N3): Maps to "reason; intellect; self-control; sanity; rational mind" and is used when Refers to reason, intellect, self-control, sanity, or the rational mind that suppresses emotional impulses to make logical and moral decisions. Often used as 理性を失う.
- いわく (いわく (iwaku) - Level: N2): Maps to "reason, cause, history, legend (often with a negative connotation or mystery)" and is used when Often used to introduce something mysterious, suspicious, or with a specific backstory. Can also mean 'according to...' when quoting someone, often with skepticism..
- 所以 (ゆえん (yuen) - Level: N1): Maps to "reason; cause; origin; source; the reason why..." and is used when A formal and somewhat literary term. Often used in the pattern 「〜の所以」 or 「〜する所以」 to explain the fundamental reason, origin, or essence of something, implying 'the very reason why something is as it is'..
- 国家理性 (こっかりせい (kokkarisei) - Level: C2): Maps to "reason of state / raison d'état" and is used when Essential structural term in CEFR C2 vocabulary syllabus..
Context for "理由"
遅刻した理由を教えてください。
Please tell me the reason for being late.
Context for "理性"
激しい怒りを感じたとしても、感情のままに行動せず、_______を保って冷静に対処することが求められます。
Even if one feels intense anger, they are required to maintain reason and handle it calmly without acting on emotion.
Context for "いわく"
その屋敷にはいわくがあると言われている。
It is said that there is a story/mystery behind that mansion.
Context for "所以"
彼が成功した所以は、たゆまぬ努力にあった。
The reason he succeeded was his tireless effort.
Context for "国家理性"
私は国家理性に興味があります。
I am interested in reason of state / raison d'état.
Synonym Mastery Challenge
Which Japanese word perfectly fits this blank space?
Fill in the blank: "遅刻した ＿＿＿ を教えてください。" (Meaning: "Please tell me the reason for being late.")
🎉 Correct Answer!
Remember: "理由" is correct here because it represents "reason, motive" in the context: "Please tell me the reason for being late.".