Then there's "rolls" vs. "buns."
The things that burgers and hot dogs are served on can be either "rolls" or "buns." So can the yummy cinnamon things served for breakfast (cinnamon rolls/cinnamon buns).
However, the single-serving bread things that are served with dinner are always rolls, never buns. Ditto the hard roll, kaiser roll or bulkie roll (I think Bulkie is/was a brand name in New England), which is round and crusty like a hamburger bun, but bigger, and the sub/hoagie roll.
This is all based on my own experience in the Northeastern U.S.
BTW, feel free to compliment me on my buns. But not my rolls!