Some things can only have certain sizes ("inflexible size"), for example Lego Duplo are a multiple of about 16 mm (I think). Other things are "flexible in size", as they don't have a restriction, or much less restrictions.

Maybe flexible isn't the right / best word either?

My use case is a bit technical, it's a computer science problem. The "inflexible size" applies to certain things (hash tables) that can only be of a size 2^n, for example 2, 4, 8, 16, 32, 64,..., 1024,... The "flexible size" ones can have any size that is a whole number, that is, 1, 2, 3, 4,... 1000,...

Maybe "flexible sized" would work, but I hope there is shorter word.

Sample usage: there is something called the "Cuckoo Filter" which is inflexible in size, that is, can only have size 2, 4, 8,... "The Cuckoo Filter is a probabilistic data structure that supports fast set membership testing." Now I need a use a different term for "Cuckoo Filter with flexible size". But "Flexible Cuckoo Filter" doesn't say it's about size, and "Flexible Sized Cuckoo Filter" is quite long.

  • You only mean variable size rather.
    – Kris
    Oct 11, 2018 at 8:18
  • Unconstrained. It is variable if that value can change, for instance, during an iterative process. It is currently constrained to be 2^n. In your case, it is unconstrained. This is a slight bend of the rules, as it is still constrained to have n as a positive integer, but is implicit as a hash list can't have partial values, so the constraint doesn't come from the algorithm.
    – jimm101
    Oct 11, 2018 at 10:29
  • @jimm101 "Unconstrained size", yes that makes sense, it might be better than "flexible size". Oct 11, 2018 at 11:33
  • 1
    @Kris variable in my view also applies to 2^n sizes... Oct 11, 2018 at 11:35

1 Answer 1


So far as I know, there is no word or phrase for such a feature of sizing. So what I am suggesting has no basis in usage. It is just interesting.

What has happened in the recent past is either that a word has been coined (‘google’, ‘hash-tag’ ...) or an expression has been adopted, which often is then converted into some acronym.

In your case, the expression that springs to mind is something like ‘fixed sequence sizing’ [FSS] or ‘sizing according to fixed sequence’ [SAFS].

It may catch on, or it may not. Until it does, it has to be redefined each time it is used!

  • That's a great idea! Yes in my case that can be used, [FS] for "flexible size" "Cuckoo [FS]", "Blocked Bloom [FS]",... Oct 11, 2018 at 7:57

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