What's the difference between 事由 "jiyuu" and 理由 "riyuu"? Both are translated to mean "reason", as in why something happened.

I even noticed in Tae Kim's Grammar Guide that both words are listed, and both are translated "reason", but no distinction is made between them.

1 Answer 1


Just for future reference, these type of questions always have the same answer:

Look at the 漢字 in these words. 事 means "thing, matter", whereas 理 is "principle, logic". Thus 事由 is a cause in the circumstantial sense, but a 理由 is a reason in the logical sense.

That said, 事由 sounds more formal and 理由 is certainly the more common word. (In spoken language, it is also possible to mistake 事由 for 自由, which is also a very common word. Yet another reason to use 理由 over 事由.)

  • I did look up the kanji but it didn't shed any light for me. And your second paragraph, alas, doesn't clarify for me either. But for now I'm content to call it that 事由 is a more formal synonym of 理由. Come to mention it, in my fruitless Google searching I did some across 事由 a lot on some legal-type Web pages.
    – JB318
    May 13, 2013 at 0:03
  • In the Japanese dictionary (大辞林), it says "事柄の起こった理由".
    – Earthliŋ
    May 13, 2013 at 0:09
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    "Just for future reference, these type of questions always have the same answer:" What do you mean by this? That you can always infer the meaning of a 熟語 from it's 漢字? That you can always infer nuances of synonyms by looking at their 漢字?
    – dainichi
    May 13, 2013 at 1:38
  • 1
  • 5
    Kanji do not always hold the real contemporary meaning of words. It is sometimes better to look for the real usage. Preferably not Google but some proper collection of examples. For example, the Tanaka Corpus accessible through WWWJDIC, or alc.co.jp search.
    – firtree
    May 13, 2013 at 6:01

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