What is Fukura in Japanese Katana terminology?

The term "Fukura" (ふくら, ふくら) refers to the curved part of the tip (Kissaki) of a Japanese sword, specifically the curve that connects the Yokote (the line separating the blade and the tip) and the tip. If this curve has a roundness or fullness, it is described as "Fukura-tsuku". If it is more linear, it is described as "Fukura-kareru". A sword with no curve at all, almost a straight line, is referred to as "Kamasu Kissaki". These terms are used to describe the specific characteristics of the sword's structure, contributing to its overall aesthetic and functional design.