Silvanis, I won't argue, but since the time of the Roman Empire, there have been fairly precise definitions. An empire differs from a simple state precisely in that it contains a collection of nationalities, different in both language and culture. You can call yourself an Empire, but only for self-aggrandizement. Of course, you will be called what you call yourself, but in a historical context, to be called an empire, there need to be fairly serious grounds. And that makes sense, agree, and there is no point in arguing about this. You can refer to anyone you like, but the fact remains. An empire and a simple state are different things. By the way, regarding the Chinese, there have historically been various ethnic groups present (remember Gumilev).