My favorite thing about Civ VI so far is how amazingly well everything is documented. Whereas in Civ IV the Civilopedia offered an exhaustive definition and explanation of every possible game concept and distinction (and all this was repeated on the wiki), Civ VI takes the far superior approach of documenting virtually nothing.
So, the mathematics eureka is defined as "build 3 different specialty districts". OK. No problem. I build a bath (aqueduct), several encampments, and a few commercial hubs. That's three different types of districts.
No eureka. I can only assume that one or more of the above is not a "specialty district". Assuming I'm correct, and a "specialty district" is a distinct subclass of district, this should be defined and its members enumerated in the wiki.
So, the mathematics eureka is defined as "build 3 different specialty districts". OK. No problem. I build a bath (aqueduct), several encampments, and a few commercial hubs. That's three different types of districts.
No eureka. I can only assume that one or more of the above is not a "specialty district". Assuming I'm correct, and a "specialty district" is a distinct subclass of district, this should be defined and its members enumerated in the wiki.