Natures only appear in the Third and Fourth Generations. Natures are like Abilities; they are automatic. However, Natures raise a certain stat while lowering another stat, or they could have no stat changes at all. The change will be 10% in either direction. Also, all Pokémon can randomly have any Nature from the list below, while each Pokémon can only have one or two Abilities assigned to them. Natures are like IVs in a way. If you want a Pokémon with a specific Nature, it is very hard to do so because natures are determined at random, but still possible since Natures are not hidden details, and there are fewer Natures than there are IVs. Natures are important because they give a boost in your Pokémon's strengths. If you own a Machamp, you would love a 10% boost in Attack while would not mind a 10% decrease in Special Attack. This would occur with the Adamant nature. Below is a list of Natures in the order of what stat they increase, and what stat they decrease.
| Nature | Bonus | Penalty |
|---|---|---|
| Bashful | No change | No change |
| Docile | No change | No change |
| Hardy | No change | No change |
| Serious | No change | No change |
| Adamant | +10% Attack | -10% Special Attack |
| Brave | +10% Attack | -10% Speed |
| Lonely | +10% Attack | -10% Defense |
| Naughty | +10% Attack | -10% Special Defense |
| Bold | +10% Defense | -10% Attack |
| Impish | +10% Defense | -10% Special Attack |
| Lax | +10% Defense | -10% Special Defense |
| Relaxed | +10% Defense | -10% Speed |
| Mild | +10% Special Attack | -10% Defense |
| Modest | +10% Special Attack | -10% Attack |
| Quiet | +10% Special Attack | -10% Speed |
| Rash | +10% Special Attack | -10% Special Defense |
| Calm | +10% Special Defense | -10% Attack |
| Careful | +10% Special Defense | -10% Special Attack |
| Gentle | +10% Special Defense | -10% Defense |
| Sassy | +10% Special Defense | -10% Speed |
| Hasty | +10% Speed | -10% Defense |
| Jolly | +10% Speed | -10% Special Attack |
| Naïve | +10% Speed | -10% Special Defense |
| Timid | +10% Speed | -10% Attack |
Note that Natures do not alter a Pokémon's HP stat.