What is Mitsumune in Japanese Katana terminology?

The term ""Mitsumune"" (三つ棟, みつむね) refers to a type of ridge on a Japanese sword that has a trapezoidal shape and three surfaces. This is why it is named ""Mitsumune"", which translates to ""three ridges"". It is also known as ""Shin no Mune"" (真の棟), or ""true ridge"".

This style became mainstream along with the ""Iori Mune"" (庵棟) style from the Heian period onwards, and was made throughout the Koto (old sword) and Shinto (new sword) periods. In the Koto period, it is often seen in the works of the Soshu tradition (相州伝).

This terminology is used to describe the specific characteristics of the sword's structure, contributing to its overall aesthetic and functional design.