romance

Two thousand and eight hundred years ago, Rome was founded. From a village in the middle of Lazio, the city evolved into a Republic and in 340 BC began to expand its territory until they conquered the whole Italy and later to all Southern Europe and some lands in Africa and Asia Minor. In 4th Century AD, the Western Roman Empire collapsed and the area it occupied was then occupied by the Germanic invaders.

It's no news, I know. When conquering new lands, Romans introduced Latin into the conquered lands. In some places, like today's France, Spain, Portugal and Italy, Latin (despite the fall of the Empire) continued to be used. However, since there were no longer a central power (the Empire), Latin lost its unity. Distinct dialects differentiate into distinct languages*. Note that I'm not saying that the invasions forced Latin to change. Latin was already changing (and it never stopped changing) and we do have accounts from first and second century AD about deviations of the popular Latin from standard (classic) Latin.

Two thousand years after Latin was spread throughout Europe, we have now many languages derived from it. Italian, French, Spanish, Portuguese, Romanian and Catalan, but also less known languages such as Galician, Asturian, Occitan, Sicilian and many others.

Not that this case is special. Contrarily, it is the rule, with no exception, for all languages in the world. They change and in one thousand years they can become unrecognizable. If it happens to be a language spread throughout a great territory, such as Latin, distinct dialects will see their differences grow until speaker of one of them cannot understand the speaker of the other dialect. However, if a language is confined to a smaller territory (and the group of speakers have a more integrated society), the changes in one dialect will eventually "contaminate" other dialect and the language will evolve more uniformly. That is more or less the case of Greek (from Ancient Greek to Modern Greek, two completely different languages) or most modern national languages (in a shorter time span, such as two hundred years).

Anyway, language change over time, always. For instance, try read a text written in English (or in your own language) fifty or one hundred years ago. Although you can understand most of it, it's clearly not the same language you speak today.

Finally, it nice to remark that although the linguistic change from Latin to Romance languages is not special at all, is very interesting since it is the most documented case of a linguistic change over time. Latin is fully documented with a phonetic-based alphabet (contrarily to Chinese, for instance) and so are the Romance languages since the 9th century.

Note:
* I won't discuss in this post the distinction between language and dialect which is, after all, quite arbitrary.