Type

A type (Japanese: タイプ Type) is a property for and their moves. Each type has three properties: which types of Pokémon it is super effective against, which types of Pokémon it is not very effective against, and which types of Pokémon it is completely ineffective against. There are 17 types, each of which is listed to the right. During Generation I, types were occasionally referred to as elements.

A Pokémon may have either one or two types. For instance, is a Fire type, while  is both a Grass type and a Poison type. With the current 17-type system, there are a possible 289 different type combinations; however, since order is unimportant, there are 153 effective type combinations. Currently there are 108 different type combinations. A move may have only one type.

Most Gym Leaders, members of the Elite Four, and some other Trainers are designed to have a type-specific theme.

Type effectiveness
If the type of a move used by a Pokémon is strong against the opponent's type, then the damage done is twice the normal amount; if a move's type is weak against a specific type, then the damage done is half the normal damage done. For Pokémon that have two types, the overall damage is calculated against both types combined.

If a move's type is completely ineffective due the opposing Pokémon's type, then the damage done by the move is zero, even if the opponent has a secondary type that would be vulnerable to it (such as, an move, on a , a Water/Ground-type Pokémon). Otherwise, the damage dealt will always be at least 1HP.

Type-affected game mechanics
When the type of an attack corresponds with one of the types of the Pokémon using it, the attack power will be increased by 50%. This type advantage is referred to as same-type attack bonus, or STAB for short. A good example is an that knows  and. Both attacks are physical attacks and both have a base power of 50. However because Aron is a Steel/Rock-typePokémon, the power of its Metal Claw move will effectively be 75.

Some weather conditions, Abilities, and held items affect moves of a certain type. , for example, causes moves to increase in power, while  causes  moves to not work on the Pokémon with this Ability. Likewise, each type has a specific item that can be given to a Pokémon to hold that will power up one of the specific types, such as the Metal Coat, which powers up moves by 20% (10% prior to Generation IV).