I have a series of items that I need to categorize. However, I would like to convey in a word that each item should really only belong to one specific category or group. Because of this intended mutual exclusivity, using the word "category" or the word "group" seems insufficient.

For example, imagine I had these items:


Possible values for acceptable 'group' names would be:


If I were to say, "To which group does 'Basketball' belong?", it's possible someone would respond by using both Sports and Color, since a basketball is orange. Words such as "bucket" or "bin" have been suggested as the implicit physical limitations of those items would help someone infer that an item can only belong to one. These seem like a good alternative.

Are there any words that are more explicit about the one-to-one nature of the grouping?

  • Welcome, but I'm sorry to inform you naming things is specifically off topic here. Please take the tour.
    – Phil Sweet
    Commented Feb 19, 2018 at 1:05
  • @mattbryanswan ... I take it you're asking for a word that means "disjoint set with a meaningful connection among its members". If that's the case, you might want to rephrase the question to fit. Commented Feb 19, 2018 at 1:27
  • Are you looking for an existing named data structure like 'Set', 'Multiset', 'List', 'Bag', Dicitonary'? It doesn't exist as a data structure label, but the generic term 'category' implies separation into mutually exclusive sets. Also, 'Group' has a technical meaning which I'm pretty sure you don't mean. 'Category' does also but that's another situation entirely.
    – Mitch
    Commented Feb 19, 2018 at 1:55
  • @PhilSweet Hi Phil! I believe my question is valid and appropriate, but my wording within my specific use case was not. I've edited the question to speak more generally. Thanks for pointing it out. Commented Feb 19, 2018 at 17:51
  • I think ‘Category’ does not imply exclusivity unless stated, @Mitch.
    – Jelila
    Commented Feb 20, 2018 at 13:27

2 Answers 2


If the main feature of the 'groups' that you want to highlight is that each is a disjoint set (an item can't be in more than one group at a time), then I'd consider using an analogous real world object's name. At the most generic level, your group is a container, but you might also consider, box, bin or bucket.

Bucket is a good choice, because nobody imagines an object being inside more than one bucket at a time, or (full) buckets within buckets, whereas containers in general can be nested. The word in already used in software design patterns like the leaky bucket precisely because of those connotations.

You could highlight that each 'group' is a particular category of thing by calling them named buckets.


Exclusive Category. Or mutually Exclusive.

You can say ‘to which single group should each of these items belong?’ This clearly means ‘each item can only go in one category.’

But you might need to explain why ‘sport’ should be chosen over ‘colour’ for basketball by saying something like ‘pick the single best group to which each item can belong’. Best then is a ‘selection criterion’.

‘Single group’ makes it very clear that they can only belong to one category.

You can use ‘single category’ in the same way.

Bucket or bag - you still need the word ‘single’ to tell people to put each item in only one bag, so I don’t think that helps at all.


  • select a single category for each item

  • place each item in only one bag

  • choose the best single category for each item

The generic term for such an assignation is still ‘single group’ or ‘single category ‘.

Another expression you can use is ‘exclusive category’ which means ‘things belonging to it cannot also belong in any other category’.

  • Place each item in one exclusive category
  • Each item belongs in an exclusive category

‘Mutually exclusive’ means that if they belong to one category, they cannot belong to another.

  • place each item in one, mutually exclusive category


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.