In a recent email conversation, an acquaintance used the expression:


Although I can vaguely infer the meaning of the expression 1対1で対応する (いちたいでたいおう), I am having a hard time finding a clear definition and description of it. All the hits in Japanese pages seem to have to do with mathematical terms (where it'd mean something like "bijective" or "one-to-one correspondence"), but our conversation had nothing to do with mathematics and the person is not a particularly mathematically-inclined person, so I doubt he'd be using it a math term for an everyday-idea... Furthermore, all the hits I got, were without that 'で' in the middle: 1対1対応する

My questions:

  • what does this expression mean in a general context? Where does it come from? How common/familiar is it?

  • which of the two forms is the correct one? is the 'で' form a typo, or just a less common form?

  • is the spelling of '1' as roman numeral standard practice, or just e-mail shorthand, with 一対一対応 being the preferred way to write it?

  • You could maybe give some context the person used it in? Seems that this is not an expression or anything, just a basic sentence. Plus, 一対一 and 対応する are not really connected.
    – oldergod
    Commented Jan 20, 2012 at 9:36
  • @oldergod: I would give more context if there were. As it is, the context is rather disconnected from the rest. I merely replaced the private topic by "それ": doubt it really has an impact. That aside, I'm pretty certain this is a set expression, not just some random use of words...
    – Dave
    Commented Jan 20, 2012 at 10:55
  • @Dave san, Oh, replaced?
    – user1016
    Commented Jan 20, 2012 at 11:10
  • 1
    一対一対応 is a mathematical term for “one-to-one correspondence,” but as Chocolate explains in the answer, the phrase you are talking about is different from it (although they are not completely unrelated). Commented Jan 20, 2012 at 12:44

1 Answer 1


・[一対一]{いったいいち}で/[一対一]{いちたいいち}で=二人きりで, one-to-one, person-to-person

・で is not a typo. We say 「一対一で対応する。」not 「一対一対応する。」

・I think both 一対一 and 1対1 are equally common, but probably the former is more formal.

一対一で対応する**(=仕事、役目、または「**さん」等の人物名・・・?)は、大変だね。= I think **(kind of work, position etc?) is such tough work, because you have to deal with someone (probably your guest, client, student etc.) person-to-person. / I guess ** would be tough, because you'd have to deal with your guest/client/student etc. person-to-person.

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