Commons:Intersectional categories
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An intersectional category (or intersection category) is a topical category which covers two or more distinct topics in one category. An intersectional category usually takes the form of "'Topic A' and 'Topic B'". Generally, each topic should be supported by its own distinct main topic category with appropriate category tree beneath it. They are usually created to combine two related topics in one place, or even to create a home for contents which belong to one of the subject topics, but have yet to be diffused. Intersectional categories differ from normal main topic categories, which have a wide variety of sub-topics and can include any contents within the main topic. Instead, intersectional categories are specific to usually two (but possibly more) specific topics, even if there are other topics that form the topics' parent topic.
- For example: Category:Trucks and buses would be an intersectional category, as opposed to the main topic category, Category:Land vehicles. This is because the while both Category:Trucks and Category:Buses are sub-categories of Category:Land vehicles, there are other land vehicle topics which would be excluded from Category:Trucks and buses.
In general, intersectional categories should be avoided, as they add aditional layers to the categorization structure without offering much real benefit. The idea is that if a user is looking for one of the subject topics, they are best served by delivering them directly to that category. The idea that Category:Trucks and buses would permit a user to find both topics in a single convenient place is not a good one, as that user would likely still in the end need to navigate to both Category:Trucks and Category:Buses to see content of both topics since only few users make use of the deepcategory search operator to see contents in multiple subcategories (e.g. by clicking on More in top right->Deepcat🖼️). Having a Category:Tall vehicles that specifies the shared characteristic is the better solution than to combine select related subjects.