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
    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
    Jan 20, 2012 at 10:55
  • @Dave san, Oh, replaced?
    – user1016
    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). 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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