As of Pokémon’s 30th anniversary, Eevee has eight official evolutions.
They are Vaporeon, Jolteon, Flareon, Espeon, Umbreon, Leafeon, Glaceon, and Sylveon. Together these forms are commonly called Eeveelutions. Each represents a different Pokémon type, giving Eevee an unusually broad evolutionary identity within the franchise.
The first three appeared in Pokémon Red, Green, and Blue through Water, Thunder, and Fire Stones. Gold and Silver added Espeon and Umbreon through friendship and time of day, while Diamond and Pearl introduced Leafeon and Glaceon. Sylveon debuted in Pokémon X and Y as a Fairy-type evolution.
Eevee itself does not evolve into every form through the same method. Evolution can depend on stones, friendship, time, location, or a known move. Regional forms and temporary battle transformations are not additional Eeveelutions, which is why those features should not be added to the total.