Climbing

Two thirds of the way down the list is il diedro, the inside corner where two walls of rock meet like an open book, and English climbers, who call it « a corner », lose the geometry that Italian keeps. Diedro is Greek: di-, two, and hédra, a seat, and by extension the face a solid rests on. Two faces, one corner. That hédra is all over English once somebody points at it. A « polyhedron » is many-faced, a « tetrahedron » four-faced. Put katá, down, in front of it and the result is kathédra, something to sit down on, which reached Latin as cathedra and meant the bishop’s throne. The church that holds one is the « cathedral » — an adjective that did the naming, with the noun it once qualified quietly dropped. From that same cathedra, worn down by French, English also has « chair ». So a cathedral, a chair and a rock feature all rest on somewhere to sit, and only the climbing word still says how many.