What do you call a subcategory of a subcategory?

Is there any particular term that can be used or should I use any other words such as group, set, collection etc.?

Edit: For Example if A is a category, B is a subcategory of A and C is a subcategory of B, what do you call C with respect to A?

6 Answers 6


Informally, a lot of people will use the word/phrase subsubcategory (or sub-sub-category).

I would advise against using it in formal writing (for formal writing use further subcategory as @Chenmunka suggested) but the meaning is completely clear and would not sound unnatural as it is used by many native speakers.


TL;DR: "Sub-subcategory" is not a thing.

In both language and taxonomy, there is no special word for the subcategory of another subcategory. There are several reasons for this.

For one, subcategory is a class of things, not a thing, itself. The prefix "sub-" indicates that all of the things in this class also belong to another, broader class of things. It does not infer how broad or narrow the parent class is.

So, grammatically, a subcategory of a subcategory is called... a subcategory.

If you have 15 levels of taxonomy, the 15th child category is still a subcategory. The 14th subcategory is both the child of the 13th subcategory and the parent of the 15th subcategory, and so on all the way up to the primary (or "main") category.

"Sub-sub-sub-(...)subcategory" is not only ugly, it literally makes no sense.

Which is perfect, because the more subcategories you make, the more confusing and bloated your taxonomy will be.

This is called diffuseness, and it defeats the point of categorising: to make sense of things.

So, if you can avoid more than two or three layers of category (primary/main category > parent subcategory > child subcategory), then you should.

It just makes sense.

  • Good answer! I'd also add that if I wanted to refer to C, I would just call it a sub-category if B (assuming that it works the same as subsets in maths.)
    – Gamora
    Jul 12, 2019 at 13:02

The phrase further subcategory is often used.

This suggests that the process of categorisation is being taken further, to a subcategory within the outer subcategory.


I suggest a diagram. Language can only take you so far before it becomes unclear. If you have to describe it in words, use "set" rather than "category".


What about: Subordinate Category, Secondary Category, Complementary Category, I think these words could be more meaningful than using sub-category of subcategory.


Category - Sub Category - Child Category

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