<human>:  Why is a Japanese sword called a katana?
<bot>: The word katana is Japanese and means “single edged”. It is named after the type of sword that is used in the Japanese samurai warrior class. A katana is a single-edged sword with a long, tapering blade and a curved, hollow-ground guard. The blade is usually made of high-carbon steel, though some are made of stainless steel. The blade is sharpened on both sides.