Latin and the Romance languages occupy a vast space along at least three dimensions: geographical, temporal, and social. Once the language of a small town on the Tiber River in Latium, Latin was carried far afield with the expansion of Roman power. The Empire reached its greatest extent under the reign of the emperor Trajan (98–117 ce), at which point it included modern-day Britain, Portugal, Spain, France, Italy, Switzerland, Austria, and the Balkan peninsula, as well as immense territories in the Eastern Mediterranean and beyond, making it by far the largest single state the Western world had ever known. Even those distances are dwarfed by the extent of Western European colonial expansion in the 1500s and 1600s, which brought Spanish to most of Latin America and the Caribbean, Portuguese to Brazil, French to Canada, and all three to their many outposts around the world, where they engendered some robust creoles. On the time dimension, the colloquial speech that underlies the Romance languages was already a constant presence during the seven centuries that saw Rome grow from village to empire – and then their history still has twenty centuries to go. Their uses in society extend to every level and facet of activity from treasured world literature to instant messaging.

A truly panoramic account of Romance linguistic history would find few readers and probably no writers. The scope has to be limited somehow. Our decision, which may disappoint some readers, is to cover five languages: French, Italian, Portuguese, Romanian, and Spanish.