Overriding translations

From Symfony docs:

Translations are not related to bundles, but to translation domains. For this reason, you can override any bundle translation file from the main translations/ directory, as long as the new file uses the same domain.

For example, to override the translations defined in the Resources/translations/FOSUserBundle.es.yml file of the FOSUserBundle, create a /translations/FOSUserBundle.es.yml file.