After the fall of the Roman empire the written language is Latin, that remains the official language of the church, diplomacy and literature. With the passing of time develops the spoken Latin that transforms continuously thanks to its everyday use and from this are born several regional Latin dialects from which will then develop the vernacular, the language of common people.
In 1200, vernacular begin to differentiate more and more from Latin and became a literary language. Il Cantico delle Creature, by San Francesco d’Assisi, is considered to be the first document of the vernacular poetic lyric, written, presumably, in 1225.
The new language gains importance more and more, thanks also to the communal civilization.
In the fourteenth century, the vernacular is becoming increasingly and to prevail among the various Italian dialects is the Tosco-fiorentino and this happens for several reasons: the greatest writers of the fourteenth century, considered the Three Crowns, write in the fiorentino vernacular, Dante, Petrarch and Boccaccio and Florence reaches the economic supremacy and cultural in all Italy.
Latin will survive for a long time, next to vernacular. In 1800 the writer Alessandro Manzoni corrects several times his work, I Promessi Sposi, to bring it to the Tuscan style and the language of this novel is example of modern writing, updating and conversational to the point to influence, in depth, the current appearance of Italian.
In 900 radio and television shape and spread Italian language. Unlike the written Italian, the common spoken Italian is a recent conquest. The use of Italian is influenced by the geographical differences and ways or regional dialects, especially concerning informal settings or family.