Briefly, vulgar (common) Latin was used throughout the Roman Empire.

Manson Alexander Stewart has written:

'A study in Latin abstract substantives' -- subject(s): Noun, Latin language, Latin language, Vulgar, Vulgar Latin language

Vulgar Latin.

Louis Furman Sas has written:

'The noun declension system in Merovingian Latin ..' -- subject(s): Declension, Latin language, Vulgar, Vulgar Latin language

All the Romance languages (Italian, French, Spanish, Portuguese and Romanian) are languages derived from vulgar Latin. Vulgar Latin was a mixture of Latin and local languages which developed in parallel with classical Latin. These evolutions were due to the fact that Latin became an extinct language and that languages evolve.