We have a UI which allows the user to specify criteria for the selection of customer records, and there's been some debate about the meaning of the term 'between'. For instance when the user seeks to find "everyone with between 2 to 4 children", should that include customers with 4 children or not?
Some of the team think that it's to do with data types - so that if dealing with integers or dates it would be inclusive at the upper end, and otherwise not. While others feel that it's more to do with cardinality so that if talking about income between 10K and 25K it would exclude the upper bound (i.e. up and including 24999, but not 25000), whereas if it was the number of bank accounts between 1 and 3, then 3 would be included.
There is a useful debate about the meaning of 'between' in Math Forum. In summary it says that instead of having, “the solution is between 10 and 20” (which is ambiguous as to whether 20 is or is not included), it may be preferable to say either “the solution is between 10 and 20 inclusively” or “the solution is from 10 through 20”. My preference is for the latter, but I'd very much appreciate the views of other UXers.