Retronym

Retronyming is the concept of modifying an object's name because the original name has changed its meaning. It is rarely known up front how long a series will last, so the initial installment is typically given a standalone title.

When applied to a movie, TV show, video game, etc., it usually consists of adding a "1" after the title of the first part of a series (in the case of Numbered Sequels), or something akin. In Real Life, this often applies to technology that has branched out from a single product. For example, the term "landline phone" didn't need to exist in 1985; there were home phones, work phones, and pay phones, but there was no need to specify that it was a hard-wired connection, because almost nobody knew of any other kind.

Happens frequently when Title: the Adaptation is involved. Things designated as "Classic", "Original" or "1/I" are very often examples.

More info on The Other Wiki. Supertrope of Franchise Driven Retitling.

Anime and Manga

 * The Japanese subtitle of the first Dragonball Z feature film, Ora no Gohan o Kaese! ("Gimme Back My Gohan!"), wasn't used until the film's home video release.
 * Many of Toei's initial film versions of their popular tokusatsu and anime franchises often got new titles when further film versions of the same franchises were made.
 * The fighting style of Kenshiro's old nemesis Shin in Fist of the North Star was originally named Nanto Seiken. Subsequent stories after published after Shin was killed off introduced various branch styles of Nanto Seiken (Nanto Suichoken, Nanto Kokakuken, Nanto Hakuroken and Nanto Ho-oken), turning "Nanto Seiken" into an umbrella term for all these martial arts. When the Hokuto no Ken Special reference guide was published in 1986, Shin's style was officially declared to be "Nanto Koshuken" to distinguish it from the general term.

Comic Books

 * The very first Sin City story was titled just that... Sin City. The series caught on, resulting in future stories containing secondary titles (i.e. Sin City: A Dame To Kill For). Even when the original story was first collected in a trade paperback format, it retained its original title. Word of God gave it the nickname The Hard Goodbye and that's what Fanon called it when discussing this particular story. When The Movie came out, the collected editions added this title. Likewise, this particular sequence in the movie shares the same title. It resulted in a slightly awkward line, however. Every story name drops its own title but this one never contained the line "the hard goodbye" since that wasn't its original name. The line was added to the dialogue in the movie.

Film

 * The first Star Wars film was originally known as just that; references to Episode IV or A New Hope were incorporated after its sequels were released. The Empire Strikes Back and Return of the Jedi have always had their respective subtitles and episode numbers in the opening plot summary.
 * Before the release of the Prequel Trilogy, the Original Trilogy was known simply as the "The Star Wars Trilogy".
 * Similarly, the video/DVD releases of Raiders of the Lost Ark retroactively retitled it "Indiana Jones and the Raiders of the Lost Ark" on their packaging, in line with the titles of the sequels. The title at the start on the movie was left unchanged though.
 * When Tron came to Blu-Ray, the case called it, "TRON: The Original Classic," so people could distinguish it from Tron: Legacy.
 * The Chronicles of Riddick: Pitch Black
 * TV broadcast prints of State Fair started using the title It Happened One Summer when the 1960s remake came out. Eventually, the critical and financial failures of the remake lessened the chances of mistaking the older movie for it, so this retronym became discarded.

Live Action Television

 * Star Trek: The Original Series
 * Happened at least twice during the Kamen Rider franchise
 * In the original 1971 series, the first Kamen Rider himself (Takeshi Hongō) was not known as Kamen Rider 1 until Kamen Rider 2 (Hayato Ichimonji) was introduced as a temporary substitute and later partner.
 * In the later 1979 series, the new Kamen Rider from that show was forced to adopt the moniker of Sky Rider after the idea of making the show a Continuity Reboot was abandoned and the older Riders started making guest appearances. The name of the series itself remained simply Kamen Rider during the rest of its original run, but later reruns and home video releases were shown as Shin Kamen Rider (The New Masked Rider) and then as Kamen Rider: Sky Rider to avoid confusion with the video movie Shin Kamen Rider Prologue.
 * The original Megazord from Mighty Morphin Power Rangers later became known as the "Dino Megazord" to distinguish it from its successors, although the name was mainly used for the 2010 reissue of the toy.
 * The Ultrabeing from Return of Ultraman was given several nicknames to distinguish him from the original Ultraman until he was officially called Ultraman Jack in the Ultraman Zoffy movie.
 * This is quite common when it comes to reality TV shows getting more seasons, usually this is just done by putting a '1' on the end (Like The Amazing Race but certain shows have done differently to match later season themes, usually by adding the place onto the end where the show was filmed.
 * The first season of Survivor has since been named Survivor Borneo.
 * The first season of The Real World has since been renamed The Real World: New York.

Literature

 * Starship Troopers has Rico's narration call military sailors on the ocean "wet navy", to disambiguate them from the Space Navy that operates the starships; other SF authors have used this as well. No term is established for what ordinary ground soldiers are called to separate them from mobile infantry. "Sitting ducks" comes to mind.

Toys

 * When Hasbro created the Transformers Generation 2 line in 1993, fans started to refer to pre-1993 era as Generation 1. Eventually, Hasbro began to use it as an official name as well.

Video Games

 * Colossal Cave Adventure -- originally just called "Adventure"; called what it is now so as not to be confused with other games, inc. the Atari 2600 classic.
 * The first Battletoads game for the Game Boy was not a port of the NES original, but an entirely new game. When the NES game was later ported to the Game Boy, it was retitled Battletoads in Ragnarok's World.
 * Subverted by Command & Conquer: Tiberian Dawn, which was officialy known as such, but was almost always referred to as "Command and Conquer" until the release of Tiberian Sun. Played straight whenever you refer to the N64 version as TD, though, as it was always just called "Command and Conquer".
 * The canceled first version of Resident Evil 2 was retitled Resident Evil 1.5. to distinguish it from the actually released game.
 * The PSP version of the first Star Ocean is known as Star Ocean 1: First Departure.

Web Original

 * One of Winston Rowntree's The 4 Reasons We Fall in Love With a Piece of Pop Culture is that it's "porn", which he defines as any cultural work "that you seek out to animalistically fill a specific need." He runs through a bunch of things jokingly called porn, coining the retronym "Sex Porn" in the process.

Western Animation

 * Lampshaded in one of The Simpsons's Halloween specials. The story takes place in the 1930s depression era, where Grandpa Simpson states that times haven't been this bad since World War One. This leads Lenny to remark why he keeps calling it that, followed by his response "Oh, you'll see!"
 * The Return of Jafar, the Pilot Movie for Aladdin: The Series, came to DVD with a case adding Aladdin's name at the beginning of the title.

Real Life

 * PlayStation One (also known as PS1 or the Updated Rerelease PSOne)
 * An inversion: the original PlayStation was once commonly referred by the gaming media as the PSX, a holdover from its development days back when it was called the "PlayStation X". Sony later used the PSX name for a DVD-R recorder that played Play Station 1 and PlayStation 2 games, much to the confusion of people who still used the PSX abbreviation when referring to the original PlayStation.
 * The first two Super Bowls were known at the time as the AFL-NFL Championship Game. The catchier name came about when one of the team owners saw his child playing with a rubber toy called a Super Ball.
 * Acoustic guitar (only called such after the electric kind was invented)
 * Corded phone and landline
 * Terrestrial radio (which would've been an oxymoron if "satellite radio" hadn't been invented)
 * Analog broadcasting (only called such after digital broadcasting became conceivable)
 * Any food with "original flavor" included on the label
 * Coca-Cola Classic
 * World War I (known at the time as "The Great War" or "The War to End All Wars" until the sequel came out). Perhaps ironically it was still occasionally called "The First World War" before the second world war happened, because it was truly the first war of its like in history at that time, not because anyone was sure there'd be a second.
 * Still photography ("still" wasn't necessary until video cameras became common in American homes.)
 * Snail mail (once e-mailing was invented)
 * "Dial-up internet" was a redundancy before the rise of DSL and cable-based high speed internet services.
 * "Internal combustion engine" appears to be a near-future example. The term is creeping up in technical conversations as electric cars, hybrid drives, and alternative fuels become more common. Internal combustion was on the other side of this when it was the new technology; up until then all "engines" in common use were external combustion steam engines.
 * Standard Definition as opposed to Enhanced and High Definition video and audio standards.
 * Which is interesting, as the first electric televisions were called "high-definition" to distinguish them from earlier mechanical televisions, leading to this odd plaque.
 * Incandescent light bulbs. Technically, that's always been their proper name, but no-one ever called them that because there weren't any other kinds available.
 * The iPod was originally called just that. While other models branched out, the core iPod line was still called iPod, until the arrival of the Video iPod. Then, when the iPod Touch came out, the Video iPod was renamed to iPod Classic (likely because other models can play videos now).