hypothermia

Winter has a way of making tiny prefixes feel heroic. In hypothermia, the Greek hupo- means “under,” and thermē means “heat,” so the word is literally heat-underflow — a medical term that feels like a radiator gone silent. The heat piece has deep Indo-European roots too: the same family gave English thermal, thermometer, and thermostat, all the gadgets and words we use when we’re trying to keep warmth on a leash. Doctors were using the term by 1877, when modern medicine loved building precise labels out of Greek bricks, and this one is wonderfully blunt: not enough heat, period. Put it beside hyperthermia and you can hear the same engine in reverse — one word says too little fire, the other too much. Either way, the body is a furnace, and hypothermia is what happens when the flame drops below the line where life starts to stutter.