n car window. Largely obsolete – most seen in modern English inside the term “quarterlights,” which is used to refer to those small windows a little ahead of the front door windows, near where the mirrors are attached. “Light” is used in the U.S. architecturally to refer to the individual panes of a split window. The etymology of the term is nautical – small prisms were inserted in the decks of sailing ships to improve visibility below deck, and these themselves became known as “lights.”