Huh, I never noticed that before. I think it's normally unambiguous because people don't normally say the opposites.

(I wouldn't always ask about "ordered collection" -- most likely it would be clear from context you were generalising pair or generalising list, but if it wasn't clear I'd ask.)

In this case, the context came from me rather than the API, as it were. As closely as I can reconstruct the thought process that led to the misunderstanding, I started by thinking "What I really want here is a thing just like a Python dictionary except that items() and keys() and viewitems() and so forth all reliably return the elements in sorted order", and then I vaguely recalled that there was a thing called collections.OrderedDict, and I assumed that must be the right thing because at that moment it hadn't occurred to me that it might mean anything else. And then I coded for days based on that assumption before getting to the point where the misunderstanding actually caused a problem (although, with hindsight, evidence of it had been visible for a while).

I guess you missed out on the near-intractable arguments prior to the introduction of OrderedDict as to exactly what an "ordered dictionary" meant. I think in the end the interpretation that won out did so because the behaviour you want is pretty easy to get with sorted(dict.keys()) etc, rather than it being more obvious or useful.