coagulation

This is one of those wonderfully sticky medical words that started out in Latin kitchens, not laboratories. Roman writers used coagulare for milk turning into curds, the same basic shock you get when cream suddenly becomes something else. English picked up the noun by around 1400, long before doctors were talking about platelets and fibrin, so the word first lived in a much more ordinary world of spoiled milk and kitchen chemistry. That’s why serum and coagulation feel like close cousins: one is the watery part left behind, the other is what sets up and separates out. Put them together and you can almost see the ancient bowl on the table, with liquid on top and a lump forming below.