History doesn't work that way. You can't define something by just listing examples of it. When has it been established that the above listed are civilizations. You need to first define what a civilization is, and then explain why the above civilizations satisfy the parameters of your definition. That's how it works.
If so, define the term "capital city".
Many historical cities we now consider capitals weren't exactly what we mean when we say capital.
Today a capital is a center of government or a place who represents the state culturali and politically.
But when we talk about historical capital cities, some of them didn't fit those terms.
Still, we call them capitals.
Because the general atmosphere around them and their role was of centrality and importance.
It's a bit more intangible and not always simple or scientifical.
This is because a capital city is a historical term, and many ancient cultures weren't fimiliar with it.
The same happens with civilizations.
There is a basic definition. Of course. (culture, political entity, ethnic origin...)
But there are some civilizations which you can consider as civilizations by looking at their history, even if they didn't fit all of the terms. (only a few civilizations are like that, but still there are).
As one of you said, a civilization is a historical term. Not a political, cultural, or ethnic term.
So many civilizations are also "tested" by their "role" in history.
This is another main reason to consider Rome and Italy as different civilizations.
I'm not yet sure about it, but I think I can also consider Franks and French as different civilizations the same way.
Most civilizations fit perfectly to the terms, like Chinese, Portuguese, Russians, Sumerians, Japanese, Hittites, Koreans, Egyptians, Assyrians, Bulgarians, Incans, Mongols, and so on.
But there are others who need some consideration: the difference between Hellenists and Greeks, the difference between Romans and Byzantines, the difference between the main 3 Scandianvian groups, the difference between Turkic groups.
This is why this thread was started. To discuss the exceptionals. Not to find a wide and perfect term for all civilizations. Because you simply can't find one.