I've been told by my teachers not to use んです and から/ので together, but I encounter them sometimes, both by sight and by ear. When I try to use it myself, it's always marked wrong.

For example, I am quite sure the sentence 10時半のバスに乗るんだから、早く支度しなさい。in this link would be considered incorrect by my teacher, but it's stated to be correct here.

jgram also states that んです should never be used with other words/ constructions that also indicate reason, like から、ので、ものですから.

Which of the following are grammatically sound?

んですから / んだから

んですので / んだので

んものですから / んものだから

[I am not sure which tags to place on this question; please advise]

  • Actually most native can use both alike depending on the stems/roots connecting to those featured forms. They all grammatically correct because all the んs are 撥音便 (N-euphony) nasal sound change from の. So I think the tag should be 'proper N euphonic changes' – Wataru 'Watson' Subridge Mar 11 '17 at 13:56
  • I don't think there is such a tag, but I've added spoken-language after what you said. Thanks! Euphonic changes of no to n aside, is it acceptable to use ん + です (which indicates reason already) with another construction to indicate reason? – rhyaeris Mar 11 '17 at 19:09
  • Actually in my dialect, like in んです+から/けん form, you can often hear...it is inappropriate in JST grammar. Anyway I will attempt answering this question later. – Wataru 'Watson' Subridge Mar 12 '17 at 1:51


This sentence would sound O.K. and even fairly natural, if not perfect, if it were uttered by a busy mom in an informal situation. Grammarians might disagree here, but it is something you would actually hear native speakers say in real life. The average speaker is not a grammarian.

If you said 「乗るから」 instead of 「乗るんだから」, then it would probably satisfy everyone. But who speaks his native language to satisfy everyone?

Interestingly, though, it would sound 100% natural (instead of just 90% as it does now) if you switched the two clauses and uttered them as two sentences as in:


That would just wipe out the small amount of awkwardness of the original sentence above.

Moving on...

Which of the following are grammatically sound?

んですから / んだから

んですので / んだので

んものですから / んものだから

んですから and んだから are unquestionably sound.

んだので is sound in 飲{の}んだので, 死{し}んだので, etc. but you cannot say 「乗るんだので」.

んものですから and んものだから are simply out of the question.

  • Thank you for the useful information and clear reply! I think I see that んだので is usable only as part of a verb's te-form. – rhyaeris Mar 26 '17 at 14:18

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