What is Machi in Japanese Katana terminology?

The term "Machi" (区, まち) refers to the boundary between the tang (Nakago) and the blade (Kami) of a Japanese sword. This area is recessed in a hook shape (Kagigata) to form the tang. The side of the blade is referred to as "Hamachi" (刃区, はまち), and the ridge side is referred to as "Munemachi" (棟区, むねまち). Typically, the Machi is hidden beneath the Habaki, a metal collar used to keep the sword from falling out of the scabbard. This terminology is used to describe the specific characteristics of the sword's structure, contributing to its overall aesthetic and functional design.