If you take the Roman empire as a country then they used Latin as a 'universal language' although in everyday use people probably continued to speak local languages. This offical Latin evolved gradually into French, Italian, Spanish, Catalan and other languages known collectively as the 'romance' languages. And as Tigerlily points out, Latin was the writing used by those who could read and write ie priests and monks, so Latin continued to be the language used by law, medicine and politics in some cases right up to today.