single word requests - "Order of magnitude" for qualitative changes
The phrase "order of magnitude" is used to indicate differences between quantities in terms of exponential powers. I've also seen it to indicate Big-Oh differences in algorithm run times.
However, in computer science there is also a notion of classifying problems in terms of their qualitative difficulty. This is the categorization of P, NP, NP Hard, NP Complete, etc. I don't think saying that an NP problem is an "order of magnitude" harder than a P problem is well-defined. Is there a different phrase which suggests the qualitative jump in problem difficulty?
Answer
I think level is a suitable word.
Specifically in the context of the polynomial hierarchy, one might informally think of a problem known to be NP-complete as one level harder than a problem in P (provided of course the hierarchy does not collapse at this level).
More generally, level generally connotes stratification in terms of achievement/difficulty. It's a gamey word, for example: your average computer game addict is usually fairly obsessed with the level achieved so far.
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