From Bulbapedia, the community-driven Pokémon encyclopedia.
A chapter is a story arc of the Pokémon Adventures manga, equivalent to the anime's seasons. They divide the manga into sections, which have a separate plot, though the characters and events from one chapter may be used in another, later chapter. Each chapter is named after a core series game, and the characters introduced in each chapter generally share those names.
Chapters are further broken down into volumes, which are then separated into rounds. There is no definitive number of rounds in each chapter.
So far, thirteen chapters have been released, of which first eight were fully translated into English and published by Chuang Yi. The beginning of the HeartGold & SoulSilver chapter, Volume 41, was also translated, however; this was Chuang Yi's last Pokémon Adventures volume to be released, as the company has since ceased operations. However, in August 2014 Shogakukan Asia, Shogakukan's official subsidiary in Singapore, has continued the release with Volume 42, having finished the HeartGold & SoulSilver chapter and is currently translating the Black & White chapter.
VIZ Media has fully translated and published the first nine chapters. The company translated the Diamond & Pearl and Platinum chapters as a separately numbered series, titled Pokémon Adventures: Diamond and Pearl/Platinum. The company has released the Black & White chapter as two separate numbered series, titled Pokémon Black and White (mini-volumes) and Pokémon Adventures: Black & White (tankōbon-sized volumes). VIZ Media also released the HeartGold & SoulSilver chapter as a fourth separately numbered series during the latter half of 2013 under the name Pokémon Adventures: HeartGold and SoulSilver. Currently VIZ is releasing X & Y chapter in a mini-volume format since December 2014 as Pokémon XY, which is similar to their previous Black and White release.
List of chapters