[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/fx.png]]
[[caption-width-right:350:(L-R) Victoria, Amber, Krystal, Sulli, Luna]]

''f(x)'' is a South KoreanPopMusic GirlGroup formed in 2009 by Creator/SMEntertainment. The name is a play on the mathematical notation for function, with "f" signifying "flower" and "x" representing the female's double X chromosome. The group members have also been nicknamed "function girls".

The quartet consists of [[TheLeader Victoria]], [[{{Bifauxnen}} Amber]], [[GenkiGirl Luna]], and youngest [[NotSoStoic Krystal]], who is coincidentally the younger sister of former Music/GirlsGeneration's Jessica.

Former member Creator/{{Sulli}} went on a hiatus from mid-2014 due to the stress of dealing with malicious internet comments about her, and eventually she officially withdrew from the group in August 2015 to focus on her acting career. Tragically, she [[https://www.nytimes.com/2019/10/14/arts/music/sulli-dead.html committed suicide in October 2019]] due to the non-stop hate she had received from the general public.

The group debuted on September 5, 2009 with the release of the single ''La Cha Ta''. The lead single off their album ''Pinocchio'' gained their first music program win and was their first song to win the triple crown.

f(x) became the first South Korean group to perform at SXSW and they also did a video with actress Creator/AnnaKendrick for Creator/FunnyOrDie, both events of which has more or less garnered attention to f(x) in the US.

Following a three-year hiatus and a brief partial reunion (without Victoria) for three SMTOWN performances, Amber made an announcement on September 1, 2019 that she had not renewed her contract with SM Entertainment. Four days later, SM announced that neither Luna nor Victoria had renewed their contracts. When asked if that mean the group had disbanded, Amber said that the group had no intentions to reunite, continuing "[w]hether we do music or not, I think there will be a time when we can but I think right now we’re just figuring ourselves out. We have no plans, but it’s never not an option." On August 18, 2020, Krystal was reported to have parted ways with SM Entertainment; her departure was confirmed in October 2020. The members have since shifted their focus to solo projects and acting work, rendering the group's future uncertain.

In 2022, Luna was cast as the lead in the Broadway musical Theatre/{{KPOP}}.


For the network owned by Creator/{{Disney}}, see Creator/FXNetworks.

[[folder: Members]]
'''Current:'''
* Victoria (Song Qian, born February 2, 1987) - [[TheLeader Leader]], Main Dancer, Lead Rapper, Vocalist
* Amber (Amber Josephine Liu[[note]]Chinese name Liu Yi Yun[[/note]], born September 18, 1992) - Main Rapper, Vocalist
* Luna (Park Sunyoung, born August 12, 1993) - Main Vocalist, Lead Dancer
* Krystal (Chrystal Soo Jung[[note]]Korean name Jung Soo Jung[[/note]], born October 24, 1994) - Lead Vocalist, Visual, Face of the Group, Maknae
'''Former:'''
* Creator/{{Sulli}} (Choi Jinri, born March 29, 1994; died October 14, 2019) - Vocalist, Lead Rapper, Visual, Face of The Group
[[/folder]]
[[folder: Discography]]
'''Korean Discography:'''
* ''LA chA TA'' single (2009)
* ''Chu~'' single (2009)
* ''Nu ABO'' EP (2010)
* ''Pinocchio'' (2011)
* ''Hot Summer'' (''Pinocchio'' repackage, 2011)
* ''Electric Shock'' EP (2012)
* ''Pink Tape'' (2013)
* ''Red Light'' (2014)
* ''4 WALLS'' (2015)
'''Japanese Discography:'''
* ''Hot Summer'' single (2012)
* ''SUMMER SPECIAL Pinocchio/Hot Summer'' (2015)
* ''4 Walls / COWBOY'' (2016)
[[/folder]]
----
!!Tropes related to f(x):

* AffectionateNickname: The members call Luna "puppy" and Amber "koala".
%% * AfraidOfNeedles: Victoria.
* AnimalMotifs
** Amber once said in an interview that she's a Koala, Victoria’s a hamster, Krystal’s a tadpole, Sulli was a penguin, and Luna’s a puppy.
** Fans have also jokingly said that Amber resembles a llama and she's accepted it, to the point where she's adopted "llama" as her new nickname.
* AscendedMeme: The fans calling Amber "llama". It's now part of her Website/{{Twitter}} username ([[http:/twitter.com/llama_ajol llama_ajol]]).
* {{Bifauxnen}}: Amber who is a {{tomboy}} and dresses like such, which matches her pretty and androgynous looks.
* ButNotTooForeign: Krystal was born and raised in America, therefore making her Korean-American. Same for Amber, who was born and raised in America to Taiwanese parents, making her Taiwanese-American.
* ButterflyOfDeathAndRebirth: Overlapping with RuleOfSymbolism, the music video for "4 [=WALLS=]" has shots of a purple butterfly in the forest scenes and revolves around the Butterfly Effect. After Amber breaks her teacup, Krystal spills tea that Victoria eventually slips on, which brings them to a dream/alternate reality where the girls race to find answers that would prevent their fate (hinted to be death) from happening.
* CampStraight: GenderInvertedTrope with Amber. She's so boyish that people have mistaken her for a man in real life, but she is attracted to men.
* CookingDuel: There was one in the 12th episode of ''Koala'', in which Luna and Sulli (who made a rice cake soup) teamed up to go against the team of Victoria and Krystal (who made kimchi pancakes). The duel was peaceful, though.
* CoolBigSis: Amber's sister Jackie and Krystal's sister Jessica act as chill and admired sibling mentors to them.
* CosmeticAward - The reward in their last mission in ''Koala''? [[spoiler: A piece of cardboard with the words ''"End of broadcast. You have done well"''.]]
* TheCutie: Sulli was f(x)'s resident fake maknae mostly because she looked (and acted) younger than the real youngest Krystal.
* DarkerAndEdgier: Their album and title track "Red Light" has a darker concept compared to previous albums.
* DeniedFoodAsPunishment - The consequence in the 7th episode of ''Koala'', in which the first person to find the Egg Pie shop gets to buy... well, an egg pie. (In the other episodes, they sometimes compete against each other to get the prize money which would be used to buy food).
* DesignStudentsOrgasm: The [[https://www.red-dot.org/project/fx-pink-tape-20762 award-winning album packaging and design]] for ''Pink Tape'' is shaped to look like a pink VHS tape containing a film. It even comes with a photobook with photos mimicking movie screencaps with breathtaking photography in the style of Creator/WongKarWai and Creator/SofiaCoppola, complete with subtitles. The album's packaging went on to influence album packaging design in the K-Pop industry ''in general.''
** ''4 WALLS'' is less flashy than ''Pink Tape'', but the minimalistic {{Retraux}} design and color scheme gave the album a stylish, sophisticated feel. Like ''Pink Tape'', it also [[https://ifdesign.com/en/winner-ranking/project/4-walls/179435 won an award]], albeit from a different awarding group.
* DoubleMeaningTitle: ''4 Walls'' is their [[ChronologicalAlbumTitle fourth full album]] and first (and most likely only) album as a four-piece.
* FakeMemories: For 24 years, Victoria thought she was O blood type and only found out after that that her real blood type is A.
* FamilyBusiness: Krystal's older sister Jessica is also in SM and is a former member of the girl group [[Music/GirlsGeneration SNSD]].
* {{Fangirl}}:
** Amber is a big fan of Music/LinkinPark's Mike Shinoda, and when she was a kid, she tried copying his voice.
** Episode 3 of ''Jessica & Krystal'' shows that Krystal's a huge fan of Pharrell Williams, Frank Sinatra and even her sister and SNSD.
* FoodSongsAreFunny: ''Ice Cream'' at one point repeats the line "Milkshake, milkshake, actually I’m Ice cream, ice cream, vanilla ice cream".
* FriendToAllChildren: Luna gets along well with kids.
* FunWithPalindromes: Krystal's Korean name.
-->"From the front, it's Jung Soo Jung. Say it backwards and it's Jung Soo Jung. My name is Jung Soo Jung!"
* GenkiGirl - Luna. She's the "energy pill" of the group.
* GirlGroup - A KoreanPopMusic example of a girl group.
%% * GratuitousEnglish - Of course - this ''is'' a Korean group we're talking about, after all. The English lyrics are usually found in Amber's raps.
%% * HatesBeingTouched - Amber.
* MultinationalTeam - Let's have a recap: Victoria is Chinese, Amber is a Taiwanese American, Luna is Korean, as was Sulli, and Krystal is a Korean American.
* NewSoundAlbum: ''4 [=WALLS=]'', f(x)'s fourth album, was heavily centered on the electronic dance music genre.
* NotSoStoic: ''Ice Princess'' Krystal. It runs in the family. Watch f(x)'s shows and you'll find out that she and her members are actually very nice and energetic.
** AscendedMeme: Krystal proved she really was an ''Ice Princess'' by winning first place in the figure skating reality show competition ''Kim Yuna's Kiss & Cry''.
* OlderThanTheyLook - Sulli had quite the babyface, even though she was actually about 7 months older than the youngest member Krystal.
* {{Retraux}}: The style of the [[https://www.youtube.com/watch?v=r4u3BzM0rqo "art film"]] for their 2nd full-length album ''Pink Tape'' was quite vintage and hipster-like. For ''[=4 WALLS=]'', the design of the album and their outfits were influenced heavily by the 70's.
* PutOnABus:
** Amber was once absent from activities due to her ankle injury, and it went on for more than 6 months. The long absence lead fans to speculate that Amber had a dispute of sorts with SM (there were allegations she fought with another member and debated leaving, but this was never proven), thus lead people to think that f(x) would have their comeback with only four members. Fortunately that wasn't the case.
** Following massive flack she was receiving for all kinds of reasons, Sulli's hiatus from mid-2014 began in this manner with SM saying the hiatus was indefinite and she would not be leaving the group. This was averted in the end when she never returned from said hiatus, formally withdrawing from the group in 2015.
* TheReveal: Krystal revealing Amber's middle name in ''Hello f(x)'' as a surprise for many, including Amber who had no intention of revealing it. She's become okay with it since then.
* ShrinkingViolet - Krystal. On the first episode of ''Jessica & Krystal'', Jessica even revealed that when Krystal was young she would cry when people even ''looked'' at her.
* SillyLoveSong: ''Chu~'' is a ridiculously cute song about kissing, complete with lyrics like "Do it do it, chu~♥ It's true, true, true, true it’s you".
* StageNames: "Victoria" for Song Qian, "Luna" for Park Seonyoung, "Sulli" for Choi Jinri. Krystal technically counts since her birth name is actually spelt Chrystal.
* SurrealMusicVideo:
** Not an official music video, but the teaser / "art video" for ''Pink Tape''. Try to decipher what the heck's happening in the video.
** The teaser and music video for ''Red Light'' is full of confusing symbolism and artsy scenes.
** The music video for ''4 Walls'' seems to feature parallel timelines where the individual members are interchangeably beginning and completing actions (with rapid cuts between parallels), switching to a dreamlike sequence with more saturated colors and altered aspect ratio, and then back to "reality" to avert a minor disaster.
* TakeThat - To the too-high standards of the South Korean celebrity industry. Blink and you'll miss it, but here it is, from the ending credits of ''Koala'' episode 11.
-->'''Sulli''': South Korea is so picky about being skinny, that's why you can't develop/grow anymore!
-->'''Luna''': We need to have some fat!
-->'''Sulli''': Don't you agree? Everyone's so skinny!
-->'''Victoria''': We should stop here... (laughs) Please edit this out!
* TeamMom - Victoria, who cooks and does the grocery shopping for the members. She's endearingly called "Vic Umma" (mother). During her time in the show ''We Got Married'', the other members even treated her partner Nichkhun (of [=2PM=]) as their [[TeamDad dad]].
* TeenIdol: Just about everyone were in their teens when they debuted as idols.
* {{Tomboy}} - Amber, and their stylists really like to emphasize this. She prefers to dress more boyishly such as baggy shorts and loose clothing, has BoyishShortHair, and used to play a lot of sport when younger (which is how she adopted her tomboy looks in the first place). It's to the point that when she once grew her hair out it was interpreted as a GirlinessUpgrade.
* TravelogueShow:
** In ''Hello f(x)'', they went to Africa for a photoshoot, to Thailand to perform in the Pattaya Music Festival, and to Japan (along with label-mates Music/SHINee) for the ''Series/BoysBeforeFlowers'' promotion.
** There's ''Koala'', in which they went to 5 countries to promote Korea's culture - although it sometimes looked more like a [[CookingShow cooking (and eating) show]] than a travelogue show...
** ''Amazing f(x)'' had the girls travelling to New Zealand.
* {{Unperson}}: This was done to Amber when she was recovering from her ankle injury, which went for over 6 months. When f(x) was filming ''Koala'', because she wasn't part of it, video footages of the members talking about Amber were edited out and it went as far as asking a Hong Kong fanboy that they were filming to take down his poster of Amber.