OC meaning in Regional ?

Occitan (English: ; Occitan: occitan [utsiˈta], French: [ɔksitɑ̃]), also known as lenga d'òc (Occitan: [ˈleŋɡɔ ˈðɔ(k)] (listen); French: langue d'oc) by its native speakers, is a Romance language (or branch of numerous of these) spoken in Southern France, Monaco, Italy's Occitan Valleys, and Catalonia's Val d'Aran; collectively, these regions are sometimes referred to as Occitania. It is also spoken in South Italy (Calabria) in a linguistic enclave of Cosenza area (mostly Guardia Piemontese). Some include Catalan in Occitan, as the distance between this language and some Occitan dialects (such as the Gascon language) is similar to the distance among different Occitan dialects. Catalan was considered a dialect of Occitan until the end of the 19th century and still today remains its closest relative.

Occitan is an official language of Catalonia, where a subdialect of Gascon known as Aranese is spoken in the Val d'Aran. Since September 2010, the Parliament of Catalonia has considered Aranese Occitan to be the officially preferred language for use in the Val d'Aran.

Across history, the terms Limousin (Lemosin), Languedocien (Lengadocian), Gascon, and later Provençal (Provençal, Provençau or Prouvençau) have been used as synonyms for the whole of Occitan; nowadays, "Provençal" is understood mainly as the Occitan dialect spoken in Provence, in southeast France.

Unlike other Romance languages such as French or Spanish, there is no single written standard language called "Occitan", and Occitan has no official status in France, home to most of Occitania. Instead, there are competing norms for writing Occitan, some of which attempt to be pan-dialectal, whereas others are based on particular dialects. These efforts are hindered by the rapidly declining use of Occitan as a spoken language in much of southern France, as well as by the significant differences in phonology and vocabulary among different Occitan dialects.

According to the UNESCO Red Book of Endangered Languages, four of the six major dialects of Occitan (Provençal, Auvergnat, Limousin and Languedocien) are considered severely endangered, whereas the remaining two (Gascon and Vivaro-Alpine) are considered definitely endangered.