Vulgar and Classical Latin

The Classical Latin of 50 BCE was a written standard of the language that long outlived its life among regular folk. By the time of Constantine I, emperor the Roman Empire just after 300 CE, Classical Latin was quite different from regular speech that we call "Vulgar" Latin. Problematically, however, few written forms of Vulgar Latin exist. When you learned how to write Latin, you learned the Classical approach. Yet we are able to uncover how Latin had changed from early Classical to Vulgar by comparing the three major Romance families

Western Romance: Portuguese, Galician, Spanish, Catalan, Occitan, French, Romansch, Italian

Eastern Romance: Romanian

Sardianian Romance: Sardinian

Actually, there are more example languages we could list, but this is a fairly representative selection. 

Below are five randomly selected comparanda. Four of these examples can be shown to develop neatly from Classical Latin into the Romance languages. One of them was apparently lost in Vulgar Latin before Latin spread across the Roman Empire. Can you guess which one?

Classical LatinPortugueseGalicianSpanishCatalanOccitanFrenchRomanschItalianSardinianRomanian
"blood"sanguissanguesanguesangresangsangsangsangsanguesàmbanisânge
"child"libercriançanenoniñonenenfantenfantuffantbimbonígnucopil
"hand"manusmãomanmanomanmainmaunmanomànumână
"heart"corcoraçãocorazóncorazóncorcòrcœurcorcuorecòrecord
"water"aquaáguaaugaaguaaiguaaigaeauauaàcquaàbbaapă

The answer in Part Two can be found here.