Once upon a time, there used to be a difference. 2-door sedans used to have solid B-pillars and were more upright, like the 4-door sedans. Coupes tended to have more sloped roofs and by the 1950s, often hardtops (without B-pillars). The coupes generally were considered more high-end and were more expensive. But by the late 1970s, most any car with only two doors was called a coupe. Europeans held out a little longer. Mainly marketing killed the 2-door sedan, as "coupes" sold and "2-door sedans" were for grandmas.