Nihonto, or commonly known as Katana in the English community is a type of Japanese sword or longsword . In use after the 1400s, the Katana is a curved, single-edged sword traditionally used by the samurai. Pronounced [kah-tah-nah] in the kun'yomi (Japanese reading) of the kanji, the word has been adopted as a loan word by the English language; as Japanese does not have separate plural and singular forms, both "katanas" and "katana" are considered acceptable plural forms in English. During the Kamakura Period (1192-1333) the Minamoto defeated the Taira in 1185 and Minamoto Yoritomo established a new military government in Kamakura in 1192. As shogun, the highest military officer, he became the ruler of Japan.