Core series/Classification/Release Model

While releases continue to break patterns, the release of core series games tends to follow a pattern.

When a generation of Pokémon games begins, a pair of games is always released. These paired versions feature virtually the same storyline as each other, but the available Pokémon differ, and some other elements are usually slightly different. This encourages trading, as it is required in order to complete the Pokédex.

Most generations feature an "upper version" title, a follow-up game or pair of games released after the first games of the generation that takes place in the same region with added features. It typically lacks certain that were available in one or both of the original paired versions; thus, a undefined of a follow-up must link together with the original pair to complete the Pokédex as well. Until Generation V, typically only a single upper version was released; starting in Generation V, upper versions have been released in pairs. Generation VI is the only generation to entirely forgo having an upper version.

Sometimes, a secondary set of paired versions that are remakes of earlier titles may also be released.