Ah, what a happy little question! The common noun for Washington D.C. is "capital." Just like a lovely tree needs its roots, a country needs its capital to thrive and grow. So next time you think of Washington D.C., just remember it's the capital where all the happy little decisions are made.
Related Q&A：
What is a common noun for Washington D.C.？-Well, you know, a common noun for Washington D.C. could be \capital\ or \metropolis\ When we think of Washington D.C., we often refer to it as the capital of the United States. It's a major political and administrative center. Or we might call it a metropolis because it's a big, busy, and important city with all kinds of activities and people. So, those are some common nouns that could describe Washington D.C. How about that?
