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 in a year and four months since their previous EP, Cherry Bomb, which was released in June 2017.^[1] It is also their first release as a ten-member group since the addition of Jungwoo in September 2018.^[2][3] It is also the group's last release to date to feature member Winwin, as he would focus his promotions on WayV following the album's release.

Upon its 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 longer than a single week at No. 1 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.^[4] It is also the group's highest charting release on the UK and France's download albums charts and first entry on the Australian Digital Albums chart.

The album's repackage, Regulate, was released on November 23, 2018, along with its lead single, "Simon Says".^[5]

The album's theme revolves around the exploration reality and dreams. The album incorporates several genres; such as pop, dance, R&B, ballad and hip-hop.^[11]

"Regular" is described as a high-energy hip hop track with sensual Latin vibes that incorporates Spanish lyrics.^[9] Billboard noted that unlike many Korean songs re-released by K-pop bands in other languages, the English version of "Regular" differentiates itself from the Korean version through the content of their lyrics.^[11] The Korean one addresses their current state as a group trying to make its way in the world, in contrast to the hopeful, goal-oriented swagger expressed in the English alternative. While both versions focus on money, the Korean addresses the reality of their world versus the luxurious lifestyle expressed in the English.^[11][14]

The sixth track, "Interlude: Regular to Irregular" contains the music used in the video "NCT 2018 Yearbook #1" as well as a rearranged version of a future bass composition (titled "The 7th Sense – Reverse") by Korean electronica musician Hitchhiker that was performed by the sub-unit in the 2017 Mnet Asian Music Awards. The track also contains narrations done in Korean (by new member Jungwoo), Japanese (by Yuta) and Mandarin (by Winwin), as well as a verse from the American author Edgar Allan Poe's 1849 poem "A Dream Within a Dream" narrated by member Johnny. The eighth track, "Come Back", is a Korean version of the originally released Japanese track off their debut Japanese EP Chain. The bonus track, "Run Back 2 U", is the full version of the demo song originally titled "Bassbot" previously performed by NCT members Johnny, Taeyong, Yuta, Ten and Jaehyun and then-SM trainee Hansol in a pre-debut video under the company's pre-debut group SM Rookies in 2015.

Credits adapted from Naver

Credits adapted from Xiami.^[28]