From Wikipedia

Soul of the Samurai

The katana is a type of Japanese sword and is often called a "samurai sword." In a precise sense, the term katana in Japanese is applied to any kind of single-edged Japanese sword, although, incorrectly or habitually, some Japanese and Western sword lovers define katana as the standard size moderately curved (as opposed to the older "tachi" style featuring more curvature) Japanese sword with a blade length of greater than 60 cm (23.6 inches). In Portuguese the designation (spelled catana-perhaps delineated from the Japanese word when Portuguese traders first arrived in Japan) refers to a slightly shorter and wider blade, commonly used to clear paths through dense jungle, or to otherwise cut down wild vegetation.

The katana is characterized by its distinctive appearance: a curved, slender, single edged blade, circular or squared guard, and long grip to accommodate two hands. It has historically been associated with the samurai of feudal Japan, and has become renowned for its sharpness and cutting ability, to the point that its purported cutting capabilities have reached mythical status.

Katana on display at Okayama Castle.