This is the 400th most frequent Catalan word.
europeus
"Europeus" means "Europeans" in English.
In this sentence, 'europeus' is used as a noun referring to the people of Europe, 'the Europeans'.
Els europeus tenen una història cultural rica i variada.
The Europeans have a rich and varied cultural history.
Here, 'europees' is an adjective modifying 'nacions', indicating that the nations are from Europe.
Les nacions europees treballen conjuntament en diversos projectes.
The European nations work together on various projects.
In this example, 'europeus' is an adjective describing 'països', specifying that the countries are European.