Some cities have the “apolis” ending like Indianapolis, others have the “opolis” ending like Metropolis"
I realize it’s from the Greek polis, but is there a difference between opolis and apolis? Or are the letter “a” and “o” interchangeable or merely stylistic?
Given that the “a” in “Indianapolis” almost undoubtedly comes from the final “a” in “Indiana”, rather than being part of the structure of “polis”, I suspect it’s just a matter of style.
Also, other than “Minneapolis”, I can’t think of any other place names ending in -polis.
Similarly the o in metropolis likely comes from metro. One where they did seem to make a choice is Minneapolis. I’d assume that could have been Minneopolis as there’s no a there in Minnesota. Others are Annapolis and Cassopolis Michigan. so it looks like a or o
There are scores of them. Apart from those already mentioned, all of which are in the US, I can think of Adrianopolis, Constaninopolis [better known to us as Constantinople], Alexandropolis, Heliopolis, Neapolis [Naples], Persepolis, Petropolis.
The suffix is -polis. You can link this to the stem with an ‘o’ or an ‘a’, according to whichever seems more euphonious. I suspect, but I don’t know, that in the names coined by Greek-speaking cultures the choice of ‘o’ or ‘a’ is driven by the grammatical gender of the stem word, but this may not be true of modern coinages by English-speaking cultures.