Regular-Irregular

Regular-Irregular is the first studio album by South Korean boy band NCT 127, the second sub-unit of the South Korean boy band NCT. Described as a multi-genre concept album with a total of eleven tracks, the album was released by SM Entertainment on October 12, 2018, and distributed by IRIVER. This marks NCT 127's first Korean major release after a year and four months since their previous EP, Cherry Bomb, released in June 2017. It is also their first release as a ten-member group after Jungwoo was added in September 2018. It is also the group's last release to date featuring member Winwin, as he would focus his promotions on WayV following the album's release.

Upon the album release, Regular-Irregular attained commercial success in both South Korea and other countries. The album debuted atop the Gaon Album Chart and became one of the few releases to stay No. 1, longer than a single week in 2018. Additionally, it debuted at No. 86 on the US Billboard 200 in the week of October 27, 2018, thus becoming NCT 127's first entry on the chart. It is also the group's highest charting release on the UK and France's download albums charts and became their first entry on the Australian Digital Albums chart.