Most people know what a synonym is (a word that has the same or similar meaning to another word, e.g. “big” and “great”), as well as a homonym (a word that is pronounced the same as another word but differs in meaning, e.g. “steak” and “stake”).
However, a retronym is a little different. A retroynm is when a word is coined after the fact, because the original term has become inadequate. A simple example of a retronym is analog clock. Before digital clocks, all clocks were analog, and were just referred to as a clock; but after digital clocks became popular, the word clock alone was no longer specific enough.
Some more examples of retronyms are acoustic guitar
Technological advancements and developments are responsible for a lot of retronyms, as they replace existing technology with better and faster substitutes. One of my favorite retronyms is snail mail, which became a popular phrase after email came along and made our lives easier.