Languages of Catalonia
The main cause of Spanish and Catalan social bilingualism in modern Catalonia was large-scale migration from the rest of Spain during the 20th century, as Catalonia started a significant industrialization which demanded an increased workforce from elsewhere. Spanish has historically been spoken among a minority of civil servants born in other regions in Spain and among segments of the wealthiest bourgeoisie. Spanish has also been spoken as a second language by most Catalans, as it has been the only official language over long periods since the eighteenth century.
Catalan language
Catalan shares many traits with the other neighboring Romance languages (Italian, Sardinian, Occitan, and Spanish). However, despite being spoken mostly on the Iberian Peninsula, Catalan has marked differences with the Iberian Romance group (Spanish and Portuguese) in terms of pronunciation, grammar, and especially vocabulary; showing instead its closest affinity with Occitan and to a lesser extent Gallo-Romance (French, Franco-Provençal, Gallo-Italian).