理 vs 由 vs 理由

hello there!

recently i have learned the kanji 理(り)、由(ゆう)and the vocabulary word 理由(りゆう). all of these are marked as “reason.”

but surely there is more to the meaning than just reason.

what kind of reason does each refer to? is it something that just transcends English language explanation? if so, please give me a way i can understand it (by story or by other vocabulary example, please).

it is a really interesting word, as i have heard it used as the title in one of my first loved japanese songs. the lyrics specifically: 「…それでも僕らは、優しやの理由が知りたい!…」

please help me in understanding this. おしえてください。ぜひ、お願いします!


If you are talking strictly about Wanikani you didn’t learn 3 “words”, you learned 2 kanjis and one word and the only word meaning reason using those kanji in Wanikani is 理由.

Edit: Personally, I have never seen 理 and 由 as a standalone word to mean reason, but apparently it’s possible according to jisho, probably in some extremely specific context.


The kanji in 理由 express different aspects of what we mean when we say “reason” in English. (If you think about it, “reason” can mean several different things) This is just from japanese-english dictionaries so there may be more nuance there but, the first kanji expresses logical reasoning while the second expresses a cause (e.g. you left the milk out and therefore it went bad). Together they make the very common word 理由 which means a reason or motive, usually one behind someone’s actions or feelings etc.

Also keep in mind that on’yomi readings are not necessarily words on their own. 理 can be read as り by itself as a word, but this is not very common. 由, when read on its own, is よし and not ゆう. This word is also not common. Many kanji, when written alone, are read with their kun’yomi readings.

Edit: also just as an aside, ぜひ is used for invitations like “do please come in”, I believe よろしくお願いします is the phrase you’re looking for here.


whoops. let me fix that. thanks!

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i see. i forgot to point out the kanji vs vocab. whoops. hehe. anyway, thanks!

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For the meaning itself of 理由, japanese dictionary give 3 definitions, but one of them seems is a technical philosophical terms, so I’ll try to translate the two commons one (I hope I’m not too far off, they are quite difficult)

The rationale/basis on how things turned to be, the rationale basis on which things were judged
Ex: Resigning for health reasons.

2.いいわけ。which in turn is defined as そうせざるをえなかった事情を説明して、了解を求めること。「風邪を理由に休む」
Explain the circumstances that forced us to do something and seek for approval/understanding
Ex: take time off / rest for reason of a cold


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