What's the difference between "case by case" and "case to case"?

I often hear the former from my Japanese students. When I asked them where they got the phrase, they always say they learned it from their high school grammar lessons.

  • I wonder if it might be generational, much like by accident vs on accident seems to be.
    – J.R.
    Jun 27, 2015 at 9:56
  • 5
    Case by case is a well-known English idiom usually used in circumstances where an overall rule cannot be applied but where matters are considered by individual instance, i.e. case by case. I have never heard case to case.
    – WS2
    Jun 27, 2015 at 10:02

4 Answers 4


This is probably due to difficulty with prepositions, for which it is harder to learn by rules than by experience! The preposition "by" is used in "X by X" where "X" is a noun to adverbially specify that the main verb is performed to each "X" in the context one at a time. Some examples are:

one by one (one at a time)

line by line (one line at a time)

case by case (one case at a time)

day by day (one day at a time)

In contrast, the adverbial phrase "X to X" specifies that the main verb is performed to the "X"s in the context from one to another. It need not imply that all "X"s are involved, but simply conveys the process of going from one to another, usually repeatedly.

[from] house to house (repeatedly out from a house into another)

[from] time to time (occasionally)

[from] cover to cover (start of a book to the end)

  • 2
    @Shaira: I came across this again, and thought of one possible usage of "case to case", namely "The prognosis varies a lot from case to case.". Of course, here "from case to case" is used to compare different cases, whereas "case by case" is a much more commonly used phrase, which is why I didn't think of the other usage earlier.
    – user21820
    Jul 28, 2016 at 8:05

In courier service we often see advertisements claiming door-to-door delivery by which they mean they collect letters/packets from one door (residential address) and deliver it to the desired address (another door). This looks OK.

  • 1
    The existence of other phrases of the form "X-to-X" does not imply that X can be any noun at all.... "case-to-case" is not standard and does not sound correct.
    – Hellion
    Nov 27, 2016 at 4:09

In the Indian sub-continent,'on a case to case basis'is often used,especially, in offices.I don't think it sounds awkward and I don't think it's non-standard!There was a time when 'weightage'was frowned upon but now it's increasingly being used,particularly,in the Sub-continent.And,for Pete'sake,who makes the rules!A rule may vary from place to place e.g.'gotten'has no applicability in British English!


I suppose "case to case" is just a mix-up with the more common "from time to time" that is a recurring expression in legal English. I have no evidence to support "case to case" and I do not think it is generational, rather the effect of globalization impacting the language too.

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