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In "some characteristic C is what distinguishes A from B", does characteristic C belongs to A but not to B, or to B but not to A?

For example:

Imposing restrictions on the available resources is what distinguishes computational complexity from computability theory.

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The word I usually use is criterion. – Stuart P. Bentley May 31 '11 at 6:48

It can be either A or undefined, but not B.

  • Fiscal purism is what distinguishes her from other candidates. (A - she has fiscal purism)
  • Reputation is what distinguishes one brand from another. (undefined)
  • Obesity is what distinguishes my mother from yo momma. (even with clear context of The Dozens, it sounds as if the speaker is insulting his/her own mother)
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it can probably go both ways and you can regard C as a discriminant

An expression used to distinguish or separate other expressions in a quantity or equation.

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Can it go both ways? I failed to come up with an example where B, rather than A clearly possesses C. – Adam May 31 '11 at 11:44
@Adam "imposing restrictions on the available resources is what distinguishes computational complexity from computability theory AND vice-versa" :) – Paul Amerigo Pajo May 31 '11 at 13:12
Ah, you meant both ways at once. I think that's a fairly fringe use, but it is possible. I meant that my suspicion is that B and B alone is not possible, as per the original question. – Adam May 31 '11 at 13:25
@Pageman Can you give an example sentence (following the format in Tim's question) where characteristic C belongs to B alone? I can't come up with one. – Adam Jun 1 '11 at 7:42
@Pageman I would say that the use of 'respectively' changes the format of the sentence from Tim's original question. I don't think it's possible for a sentence of the form "C is what distinguishes A from B" to imply that characteristic C belongs to B alone. – Adam Jun 1 '11 at 8:38

It depends on what the subject matter is. As the subject matter changes, (C) changes in distinguishing (A) or (B).
In your case, the fact that "imposing restrictions on the available resources"(C) is an action distinguishes it from being part of "computability theory"(B), so "imposing restrictions on the available resources" belongs to "computational complexity"(A)

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