Hydrogen

The eighth entry is la plaque bipolaire, and its noun is one English borrowed and then shrank. An English « plaque » has a narrow job: the round sign on a house where somebody famous once lived, the engraved panel beside a surgery door, the film a hygienist scrapes off teeth, the deposit a cardiologist worries about in an artery. French never narrowed it. La plaque is any rigid, flat sheet of anything, whatever it happens to be for. Une plaque de cuisson is a hob, une plaque de four a baking tray, une plaque de verre a sheet of glass, une plaque de chocolat a slab of chocolate, la plaque d’immatriculation a number plate, and une plaque tectonique the plate a continent rides on. Even the figurative use stays mechanical: une plaque tournante is a railway turntable before it is a hub. So the part in this entry is a « bipolar plate », a machined sheet that carries gas across its faces and current through its thickness. Nothing is engraved on it, and « plaque » in the English version would screw a memorial into a fuel cell.