What bookdealers really mean. A dictionary by Tom Congalton and Dan Gregory (Between the Covers), with additions from other sources
The inside portion of the flexible area where book cover meets the book spine; often used interchangeably with the term joint, which should be used to designate the outside or exterior portion of the "hinge". A volume which has received heavy or rough use often has cracked or broken hinges.
Articulation du plat et du dos d’un volume.
Fals (på bogbind)
Fals (på bokpärm)
Das innere Gelenk, wo der Bucheinband mit dem Buchblock zusammengefügt ist.