This is the 528th most frequent French word.
européen
European.
In this sentence, 'européenne' is used as an adjective to describe the noun 'Union', specifying that it is related to Europe.
L'Union européenne est une institution importante.
The European Union is an important institution.
Here, 'européens' describes the noun 'plats', referring to dishes originating from Europe and uses the plural masculine form.
Certains plats européens sont très connus à travers le monde.
Certain European dishes are very well-known around the world.
In this case, 'européen' is used as a predicate adjective following the verb 'être', describing the state of being associated with Europe.