f(x) (South Korean girl group)

Members

• Victoria – leader, vocalist, born in China; active in variety and acting.
• Amber – rapper and vocalist, raised partly outside Korea; also a songwriter and solo artist.
• Luna – main vocalist, recognized for her singing and musical theater work.
• Krystal – vocalist and visual, who also established an acting career.
• Sulli – original member who left the group in 2015 to focus on acting; she died in 2019. (Sulli had taken a hiatus from group activities in 2014 prior to her departure.)

Name and musical identity

The group's name is stylized as f(x), borrowing the mathematical notation for a function. Official explanations have described it as a metaphor: the output (music and performance) changes with various inputs (members, ideas and influences). Musically, f(x) was associated with electropop, synth-pop, and experimental EDM-leaning production, often featuring unconventional song structures and sonic textures compared with mainstream K-pop of the same era.

Career highlights and releases

f(x) debuted in 2009 with the digital single "LA chA TA" and followed with a string of commercially successful singles and albums. Early hits included "Nu ABO" and "Hot Summer," while later releases showed growing critical interest for their adventurous production. Major studio albums and notable singles include:

• Singles: "LA chA TA" (2009), "Nu ABO" (2010), "Hot Summer" (2011), "Electric Shock" (2012), "Rum Pum Pum Pum" (2013), "Red Light" (2014), "4 Walls" (2015).
• Albums: Pinocchio (2011; repackaged as Hot Summer), Pink Tape (2013), Red Light (2014), 4 Walls (2015).

Among these, the 2013 release often draws attention from critics for its cohesive concept and adventurous production, and the group is frequently cited as one of the more musically experimental acts within SM Entertainment's roster during that period.

Hiatus, solo activities and legacy

From about 2014–2016 the members increasingly focused on individual projects. Sulli's announced hiatus in 2014 and formal departure in 2015 marked a turning point; the remaining four continued as a quartet before group activities slowed. Members went on to pursue solo music, acting, hosting and international projects. Some later chose not to renew contracts with the agency, and schedules and personal priorities contributed to a prolonged group hiatus.

f(x)'s legacy rests on blending pop accessibility with electronic experimentation and a distinct visual identity. They influenced other K-pop acts interested in integrating alternative electronic textures into mainstream releases and remain referenced in discussions of early 2010s K-pop that pushed stylistic boundaries.

Notable facts

1. The group mixed Korean, English and occasionally other languages in lyrics and interviews, reflecting diverse member backgrounds.
2. f(x) received several year-end and industry awards during their active years and performed on major Korean music shows and international stages.
3. Although inactive as a group, f(x) is frequently remembered for its distinct sonic identity and the individual careers its members built afterward.