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How to say "Theory" in Japanese

Both words can translate to "theory", but which should you choose?

Japanese Option A

理論

りろん (riron)
N3 / CEFR Syllabus
VS
Japanese Option B

学説

がくせつ (gakusetsu)
B2 / CEFR Syllabus

Nuance Contrast & Translation Difference

When translating "theory" into Japanese, you must choose carefully between 理論 and 学説. In Japanese, 理論 (りろん (riron)) is typically associated with "theory" (Syllabus Level: N3) and represents 専門的な内容や学問の分野で「考え方」や「法則」を示す際に使われます。英語の"theory"に相当します。. On the other hand, 学説 (がくせつ (gakusetsu)) maps to "theory (academic)" (Syllabus Level: B2) and represents Essential structural term in CEFR B2 vocabulary syllabus.. A literal translation of "theory" can often sound unnatural to native Japanese speakers if mixed up!
Bilingual Context for "理論"
彼の研究は新しい理論に基づいています。
His research is based on a new theory.
Bilingual Context for "学説"
私は学説に興味があります。
I am interested in theory (academic).

Nuance Mastery Quiz

Which Japanese word perfectly fits this blank space?

Fill in the blank: "彼の研究は新しい ___ に基づいています。" (Meaning: "His research is based on a new theory.")
🎉 Correct Answer!

Remember: "理論" fits here because it means "theory" in the context of: "His research is based on a new theory.". "学説" represents "theory (academic)".

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