2Yoon (Hangul: commonly stylized as 2YOON) is a official sub-group of South Korean girl group 4Minute, formed by Cube Entertainment in 2013. The sub-group consists of Gayoon and Jiyoon.
Gayoon and Jiyoon are the respective main and lead singers of 4minute.
The duo were known to fans collectively as Ssangyoon (a portmanteau of the Hangul for word "twins" and the last characters of their given name "yoon".) However, as the pronouncation of "Ssangyoon" involves a tensed consonant, it was deemed to be ill-fitting for the group's cute image. As such, the sub-unit was rechristened 2YOON to better reflect their charms. In addition, "ssangyoon" could be potentially misheard as a profanity, further supporting the basis for the name change.