Generation III, what changed

Generation III introduced abilities, natures and the IV and EV system

In review Under fact check; out of search until accepted.

Generation III replaced DVs and stat experience with individual values, effort values and natures. Ruby and Sapphire went on sale in Japan on 21 November 2002 for the Game Boy Advance and added 135 species for a total of 386. FireRed and LeafGreen remade the Kanto games in 2004, and Emerald followed the same year.

Generation III: Ruby, Sapphire, FireRed, LeafGreen and Emerald. Main-series games only.

Types17

Stat formulaIVs 0 to 31, EVs, nature

Physical and specialBy type

BreedingDay Care, three IVs inherited, Everstone nature in Emerald

Battle mechanicAbilities, double battles

GamesRuby, Sapphire, FireRed, LeafGreen, Emerald

The defining change

IVs, EVs and natures replaced DVs and stat experience

Individual values widened to 0 to 31 for all six stats.
Effort values replaced stat experience, capped at 510 in total and 255 per stat.
A new stat formula took IVs, EVs and nature together.
The damage roll changed to 16 values from 85 to 100 percent.

The chart stayed at 17 types

No new types arrived; the chart stayed at 17.
New species extended existing types, such as Aron, Lairon and Aggron as Steel and Rock.

The chart held and abilities bent it

Abilities changed matchups in effect, as Levitate made a Pokémon immune to Ground-type moves.

Natures and IVs began passing through breeding

Natures arrived: 25 of them, 20 raising one stat by 10 percent and lowering another.
Emerald let a female or Ditto holding an Everstone pass its nature with a 50 percent chance.
Three IVs passed from the parents to each egg.
Incense breeding produced the new baby species Azurill and Wynaut.

Abilities and double battles arrived together

Abilities arrived, 76 of them in Ruby and Sapphire.
Double battles arrived.
Hail joined the weather list, and Drizzle and Drought set weather for as long as the user stayed in.
Pokémon Contests and Secret Bases arrived.

Ruby and Sapphire cut the link to older cartridges

Ruby and Sapphire dropped the day and night cycle, keeping a clock for berries and tides.
Gender and shininess moved from DVs to a hidden personality value.
Trading with Generation I and II cartridges was impossible.

Emerald merged both villain teams and added the Battle Frontier

Ruby set Team Magma against Groudon; Sapphire set Team Aqua against Kyogre.
Emerald used both teams and Rayquaza and added the Battle Frontier with seven facilities.
FireRed and LeafGreen added the Sevii Islands and shipped with the Wireless Adapter.
The National Pokédex in Ruby and Sapphire unlocked only after trading with FireRed, LeafGreen or another unlocked game.

3 releases, 2002 to 2004

2002Ruby and SapphireGame Boy Advance
2004FireRed and LeafGreenGame Boy Advance
2004EmeraldGame Boy Advance

Type chart era

17 types in the Generations II to V chart

Battles in these games follow that chart, shared with the rest of Generations II to V. Open the type chart by era

Generation III rows add abilities and the modern stat formula

Learnset tabs Ruby-Sapphire, Emerald and FireRed-LeafGreen hold three separate lists, plus tutor moves in Emerald and FireRed-LeafGreen.
The abilities block starts at Gen III; earlier tabs show none.
Stat ranges from Gen III onward use IVs 0 to 31 and EVs to 255 per stat.