Italian evolved from the Tuscan dialect of the Latin spoken by the Roman populations in Central Italy, and was subsequently adopted throughout Italy by the process of linguistic unification of the peninsula that took place in the centuries after the fall of the Western Roman Empire in 476 AD.
Italian is the fifth most widely spoken Romance language in the world by number of native speakers, after Spanish, Portuguese, French and Italian, and the third by number of total speakers, behind Spanish and Portuguese. It is an official language of Italy, Switzerland (Ticino and the Grisons), San Marino, Vatican City and various communities in Slovenia and Croatia.
Outside of Italy, Italian communities can also be found throughout Europe, North and South America and Oceanica, as a result of the Italian diaspora; some of the areas most significantly settled by Italian immigrants include Argentina, Brazil, Canada, Switzerland, the United Kingdom, the United States, and Venezuela.
Italian is also a liturgical language of the Catholic Church, and was also traditionally the language of the diplomacy and the high culture of much of Europe and the Middle East.
The Italian language is closely related to the other Romance languages, and to a lesser extent, the other Italic languages, such as Latin and Oscan. It shares a particularly close relationship with Spanish and Portuguese, with approximately 82% lexical similarity between Italian and Spanish and approximately 79% lexical similarity between Italian and Portuguese.