District is the neutral word
Why the API uses district for counties, departments, and similar administrative areas, while keeping their local type.
I needed one field name for the administrative area below a state or region. In the US, the obvious word is county. That gets awkward as soon as the same field has to describe a French department.
I chose district. It gives the API one name for this level of place without making every country sound American. The record still says type: "county" for Guilford County and type: "department" for Paris, so the local distinction survives.
The other names didn't solve that problem. fips is a code system, and an American one at that. admin2 describes the level in GIS terminology, but it isn't a useful word for most developers to have to learn before they can look up a county.
This doesn't mean counties, departments, and British districts have identical powers or fit identical systems of government. It means your code has a consistent place to find the identifier, name, and type.
A district lookup uses the area's own code: /district/37081 for Guilford County, /district/75 for Paris. Read name for the place and type for what kind of area the record describes.