[ffindling]

Doug is correct in his definition of a roadster. Traditionally, a roadster
has no side windows. Usually, nothing at all or side curtains. A convertable
coupe has roll down side windows. The same distinction applied to open 4
door cars as well. A touring car (sometimes called a phaeton
in later years) had no side windows. Convertable sedans had roll down
side windows. Cabriolet is essentially The King's English for
convertable. As Doug mentioned, all these terms have become very
skewed in recent years such as Mercedes-Benz use of the term coupe
roadster which they apply to cars with lift-off tops as opposed to ones
with retractable tops.

....Fred