If a pokémon levels up in battle, it will not evolve until the battle is over. A pokémon can only evolve once after a battle or consuming a rare candy, even if it gained multiple levels.Behavioral and cognitive learning even if a pokémon is fainted at the end of the battle, if it leveled up when it met its evolution requirements during the battle, it will still evolve, but will not be revived from fainting.Behavioral and cognitive learning however, prior to generation VI, the player's pokémon would not evolve if player lost the battle, even if its evolution requirements were met.Behavioral and cognitive learning

All pokémon that evolve by leveling up have at least one requirement that must be met when leveled up in order to evolve, the most common being that the pokémon must be at least a specific level after leveling up.Behavioral and cognitive learning other requirements include knowing a specific move, being in a specific location, or holding a specific item. A pokémon that meets its level-up evolution requirements will always attempt to evolve when it is leveled up in battle or by using a rare candy, regardless of whether it had previously been prevented from evolving.Behavioral and cognitive learning

There are four different types of location that can trigger location-based evolutions: moss rock, ice rock, special magnetic field, and mount lanakila.Behavioral and cognitive learning mount lanakila, which is only required for crabrawler's evolution, is the only one which is a specific location rather than a type of location, due to crabrawler so far having only appeared in a single region.Behavioral and cognitive learning

With the exception of pokémon heartgold and soulsilver, in every core series game since this method was introduced, there is a location for every location-specific evolution.Behavioral and cognitive learning while no such locations exist in pokémon: let's go, pikachu! And let's go, eevee!, none of the pokémon that could be evolved into by a location-specific evolution exist.Behavioral and cognitive learning

Cosmoem will evolve into either solgaleo or lunala depending on the game it is leveled up in. Rockruff will always evolve into lycanroc, but lycanroc's form depends on the game rockruff was evolved in, and rockruff's evolution can only occur at certain times of day (midday form requires it be daytime while midnight form requires it be nighttime); furthermore, special rockruff that have own tempo can only evolve into dusk form lycanroc, which is not dependent on the game.Behavioral and cognitive learning

• burmy evolves at level 20, but its evolved form is determined by its gender and, if female, its cloak. As burmy, its cloak changes according to the place where it last battled but has no effect on burmy itself; once it evolves into wormadam, its cloak no longer changes, and its types and the moves it can learn are dependent on its cloak.Behavioral and cognitive learning

Some pokémon evolve when they are exposed to a specific evolutionary stone. The player can use an evolutionary stone on compatible pokémon at any time outside of battle.Behavioral and cognitive learning using an evolutionary stone on a pokémon consumes the item. Unlike other evolution methods, evolution by evolutionary stone cannot be prevented by holding an everstone.Behavioral and cognitive learning due to being able to evolve at any time, these pokémon usually learn fewer or no moves by level up after evolving.

The most common additional requirement is an item.Behavioral and cognitive learning all evolutions that require an evolution-inducing held item (except feebas's evolution into milotic) or a sun, shiny or dusk stone to evolve in the core series require an item to be spent in pokémon GO, in addition to the candy cost.Behavioral and cognitive learning for evolutions introduced in generation II, the item required is the same as in the core series; for evolutions introduced in generation IV, a sinnoh stone is required instead.Behavioral and cognitive learning

• once per nickname, if an eevee has one of five special nicknames when evolved, it will evolve into a specific pokémon. If the eevee is nicknamed "rainer", "sparky", "pyro", "sakura", or "tamao", it will evolve into vaporeon, jolteon, flareon, espeon, or umbreon, respectively.Behavioral and cognitive learning once the player has evolved an eevee using one of these nicknames, that nickname will no longer have any impact on eevee's evolution.