"A" is a song by South Korean girl group Rainbow. The song was released on August 12, 2010, and was later included on their second mini album So Girls.
A teaser photo with the concept of the song was released in August 4. A teaser of the music video was released in August 10 and the full music video in August 12, along with the release of the single.
The song was produced by Han Jae Ho and Kim Seung Soo (also known as Sweetune), who also produced the songs "Rock U", "Pretty Girl", "Honey", "Wanna", "Mister" and "Lupin" for their label-mate KARA.
The promotions of the song started on August 13, in the KBS's Music Bank and also promoted on MBC's Music Core, SBS's Inkigayo and Mnet's M! Countdown.
In the debut week, the song debuted at number 50 and climbed to the position 11 on the following week. The highest peak of the song is number 9, ranked in the week of September 4. The song ranked number 80 in Gaon's Yearly chart with 337,665,388 points and with 1,617,074 digital copies sold.
The song was re-record in Japanese as the group's debut single in Japan. It was released digitally on September 7, 2011 and physically on September 14 in 4 different versions: 3 limited editions (CD+DVD, CD + 32-pages photobook and CD Only + Bonus track) and a regular edition.
The Japanese version remains some lyrics written by Song Soo Yoon and was translated by Yu Shimoji and nice73. The B-side is a Japanese version of the song "Gossip Girl", previously recorded in Korean. The song is the lead single from their debut EP with same name.
In Japan, Rainbow performed the song on the shows Happy Music, Hey!Hey!Hey! Music Champ and Music Japan. The group held their first event in Tokyo's Ikebukuro district, which drew an enthusiastic crowd of 2,000 fans. They performed "A" and had a 15-minute talk session.
The physical single debuted at number 3 in Oricon's Daily chart and also number 3 in Oricon's Weekly chart with 24,082 copies sold on first week. After hearing about their debut position in Japan, the girls stated “When we first heard that we were ranked in third, we were all surprised because we had no idea that they’d take such an interest in us. There were even some members who cried. There’s also a lot of pressure in that we have to work harder and do better. We’re still very grateful and thankful for our position on the charts. Since we’re already receiving so much love, we’re really not anticipating a rise in the weekly charts. For the remainder of our stay here, we’re just going to do our best.”
The "ab dance" featured in Rainbow's choreography was banned from broadcasting on September 8, 2010 due to it being "too sexual suggestive". The dance move involves the group lifting their shirts up but only up to the point where their abdomen or stomach can be seen before lifting it down again which was deemed similar to a 'strip tease'. The music video was also age restricted on YouTube, but DSP retired the restriction. They started promoting the song without the "ab dance" in September 11.
However, when group promoted the song in Japan they were allowed again to perform the dance, and referred to it as the "belly dance".