The southernmost regions of Italy—most of Calabria, southern Apulia, and southern Salerno (Cilento region) as well as Sicily—are home to Sicilian rather than Neapolitan. Classification Neapolitan is a Romance language and is generally considered one of the Italo-Romance branch of the Italo-Dalmatian languages. There are notable differences among the various dialects, but they are all generally mutually intelligible. Italian and Neapolitan are of variable mutual comprehensibility, depending on affective and linguistic factors. There are notable grammatical differences, such as Neapolitan having nouns in the neuter form and a unique plural formation, as well as historical phonological developments, which often obscure the cognacy of lexical items. Its evolution has been similar to that of Italian and other Romance languages from their roots in Vulgar Latin. It may reflect a pre-Latin Oscan substratum, as in the pronunciation of the d sound as an r sound (rhotacism) at the beginning of a word or between two vowels: e.g. doje (feminine) or duje (masculine), meaning "two", is pronounced, and often spelled, as roje/ruje; vedé ("to see") as veré, and often spelled so; also cadé/caré ("to fall") and Madonna/Maronna). Another purported Oscan influence is the historical assimilation of the consonant cluster as , pronounced (this is generally reflected in spelling more consistently: vs Italian "world"; vs Italian "when"), along with the development of as ~ ( vs Italian "drum"), also consistently reflected in spelling. Other effects of the Oscan substratum are postulated, but substratum claims are highly controversial. As in many other languages in the Italian Peninsula, Neapolitan has an adstratum greatly influenced by other Romance languages (Catalan, Spanish and Franco-Provençal above all), Germanic languages and Greek (both ancient and modern). The language had never been standardised, and the word for tree has three different spellings: , and . Neapolitan has enjoyed a rich literary, musical and theatrical history (notably Giambattista Basile, Eduardo Scarpetta, his son Eduardo De Filippo, Salvatore Di Giacomo and Totò). Thanks to this heritage and the musical work of Renato Carosone in the 1950s, Neapolitan is still in use in popular music, even gaining national popularity in the songs of Pino Daniele and the Nuova Compagnia di Canto Popolare. The language has no official status within Italy and is not taught in schools. The University of Naples Federico II offers (from 2003) courses in Campanian Dialectology at the faculty of Sociology, whose actual aim is not to teach students to speak