One day, I asked my japanese friend how I could invite some friends to eat. He said

I know that we could also say:


but I got interested in why he used "kai".
I'd like to know others situations that japanese people use "kai"

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    As others have said, it's a typical familiar inflection. Importantly, it is a typical male inflection...
    – Dave
    Commented Aug 26, 2011 at 7:16

3 Answers 3


As opposed to 「か」, which is open-ended and can have any sort of answer, 「かい」 is expected to have an answer in the affirmative or negative only, that is, yes or no, with subsequent explanation optional.



× 誰が来たのかい

  • could you give me an example? I still can't differenciate "kai" than "ka". yoroshiku Commented Aug 26, 2011 at 2:49
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    Can't you say things like 何色が良いかい, or is this a nonstandard development?
    – Matt
    Commented Aug 26, 2011 at 4:32
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    That's my point, though... You can find examples of this sentence online, and they definitely don't mean "解". (Whereas, indeed, 誰が来たのかい" is very rare.) So the question is, are these usages nonstandard, or is the difference subtler than "yes/no vs open-ended"?
    – Matt
    Commented Aug 26, 2011 at 4:43
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    @Ignacio: It's not 解. The い is a suffix which is probably derived from よ or や, at least according to Daijisen.
    – Zhen Lin
    Commented Aug 26, 2011 at 4:50
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    can I say "一緒に行かないかい?" Commented Aug 27, 2011 at 18:29

かい is used to soften the rudeness of か in informal speech. Sentences like "見たか?" or "好きか?" are harsh to the ear, and using かい instead of か is thus nicer to the listener.

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    for an invitation, within friends among japanese people, is it normal to say かい like "行くかい" (or maybe "行けるかい")? Commented Aug 28, 2011 at 3:44
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    I mean, is it more common than 「行かない?行こうか?、、、」? Commented Aug 31, 2011 at 21:24
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    @Axioplase However since this is a "male-usage", how do female speakers soften the か ?
    – Pacerier
    Commented Mar 26, 2012 at 3:23
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    @Pacerier I think female speakers say 一緒に食べに行く? or 一緒に食べに行かない?
    – user1016
    Commented May 25, 2014 at 8:02
  • @danieltomio (行く)かい? / (行ける)かい? is less common than (行か)ない? / (行こ)うか? / (行こ)う(よ) etc. at least among young people.
    – user1016
    Commented May 25, 2014 at 13:13

I'm not so sure about the folksiness, but it's definitely very informal. I've mainly heard it used in speaking to children and intimates. I don't think it would be used toward social superiors in most situations. By the way, there's an analogous variant of the copula, だい, as in 「ママのおにぎりはどうだい?」.

  • Is there any situation I could use だい, as a foreigner speaker? would it sound weird if I say it? Commented Aug 26, 2011 at 3:32
  • @daniel tomio: yes "どうだい?" is very ok. You can use it all the time you let your friends taste that cake you made, or when you decide what time to meet at (9時は、どうだい?)
    – Axioplase
    Commented Aug 26, 2011 at 3:48

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