Retronym

A retronym is a type of neologism that provides a new name for an object or concept to differentiate its original form or version from a more recent form or version. The original name is most often augmented with an adjective (rather than being completely displaced) to account for later developments of the object or concept itself.

Much retronymy is driven by advances in technology. Examples of retronyms are "acoustic guitar" (coined when electric guitars appeared), and analog watch to distinguish from a digital watch. Often, at first, the new version of an object is given a special name to distinguish it from the established version. If, however, the new version becomes the standard, it loses the part of its name that identifies it as new or different, and a retronym is coined for the original. The earliest razors with encased blades were called "safety razors" to distinguish them from what were then just called "razors." But the safety razor has since become the standard and the original razor is now called a "straight," "open," or "cut-throat" razor.

Similarly, the first bicycles with two wheels of equal size were called "safety bicycles" because they were easier to handle than the then-dominant style that had one large wheel and one small wheel, which then became known as an "ordinary" bicycle. Now, most "bicycles" are expected to have two equally-sized wheels, and the other type has been renamed "penny-farthing" or "high-wheeler" bicycle. Prior to the introduction of pneumatic tires, riding over the large wheel of the "penny-farthing" gave a much smoother ride, which accounts for their popularity. The "penny-farthing" itself had displaced bicycles with more equal wheels. Almost at the same time the "penny-farthing" was introduced the older bicycles became known as "bone-shakers", possibly another retronym.

In the entertainment industry, this can manifest itself as calling a movie "Part 1" once sequels are released or by slightly altering the title (e.g. Star Wars Episode IV: A New Hope or Indiana Jones and the Raiders of the Lost Ark) to emphasize its connection with the sequel(s), or by referring to a television series as "the original," as in Star Trek: The Original Series.