Synonym Nuance VS
How to say "Reason" in Japanese
Both words can translate to "reason", but which should you choose?
Japanese Option A
理由
りゆう (riyū)
N4 / CEFR Syllabus
VS
Japanese Option B
所以
ゆえん (yuen)
N1 / CEFR Syllabus
Nuance Contrast & Translation Difference
When translating "reason" into Japanese, you must choose carefully between 理由 and 所以.
In Japanese, 理由 (りゆう (riyū)) is typically associated with "reason, motive" (Syllabus Level: N4) and represents A noun referring to the cause or explanation for something. Often used with なぜ.
On the other hand, 所以 (ゆえん (yuen)) maps to "reason; cause; origin; source; the reason why..." (Syllabus Level: N1) and represents 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'.. A literal translation of "reason" can often sound unnatural to native Japanese speakers if mixed up!
Bilingual 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.
Bilingual 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.
Nuance Mastery Quiz
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" fits here because it means "reason, motive" in the context of: "Please tell me the reason for being late.". "所以" represents "reason; cause; origin; source; the reason why...".