Loona (stylized as LOOΠΔ) is a South Korean girl group that is especially known for their special way of debuting. They begin their debut project in late 2016 and it ended early 2019 with the release of favOriTe. Their name in korean is "이달의 소녀" which translates to "Girl Of The Month". The first constenant of each letter has been rearranged to form LOOΠΔ. Each month for about 18 months they debuted a member that got their own solo mini album, and then in order of debut they formed mini groups (sub units). For example, the final 4 members form "LOOΠΔ yyxy". Each music video and even some b-side songs have a complex story, called the "loonaverse", where each sub unit is in a different world.