Languages of Catalonia
According to the government of Catalonia, Spanish, locally known as Castilian, is currently the most spoken language in Catalonia (45.9% daily users of Spanish vs. 35.6% daily users of Catalan vs. 11% daily users of both Spanish and Catalan) and especially in the Barcelona metropolitan area, as well as native language and usual language of many Catalan citizens. This language is widely prevalent in the press, cinema and in daily life.
Province of Castellón
It is a bilingual territory whose inhabitants speak both Spanish and the local co-official language of Valencian/Catalan. Although Spanish and Catalan are closely related comprehension is limited: the language is a 'bridge' between Western Iberian and Gallo-Italian. There are marked distinctions in vocabulary and grammar which puts Catalan closer to Occitan in southern France and Italian (in frequently used words) which make it difficult for a monolingual speaker of Spanish to understand. Usage is a source of some controversy and political but not to the degree as in Catalonia.