The Spanish people display great regional diversity. Separatist tendencies remain particularly strong among the Catalans and the Basques. Castilian is the standard Spanish language, but Catalan (akin to Provençal), Galician (akin to Portuguese), and Basque, unrelated to any other language, are still spoken and written extensively in their respective districts. Roman Catholicism was the official religion until 1978, but its role in Spanish public and private life has declined. There is a sizable Muslim minority (about 1 million), largely consisting of North African immigrants.