Sai (釵) is the Ryukyu name for a traditional Okinawan weapon also used in India, China, Indonesia, Malaysia and Thailand.
The basic form of the weapon is that of a pointed, rod-shaped baton, with two long, unsharpened projections (called tsuba) attached to the handle. The very end of the handle is called the knuckle.
Sai are constructed in a variety of forms. Traditional sai are round, while some reproductions have adapted an octagonal middle prong. The tsuba are traditionally symmetrical, however, the Manji design developed by Taira Shinken employs oppositely facing tsuba.
It is believed that the sai was always a weapon. Although some hypothesize that it originated as an agricultural tool used to measure stalks, plow fields, plant rice, or to hold cart wheels in place, evidence for this is limited.
The sai is known to have been used in other parts of Asia before its arrival on Okinawa, likely originating from Indonesia. In Malay the sai is known as a "chabang" (also spelled cabang/tjabang, meaning branch) and is thought to derive from the Indian trident. The chabang spread through the rest of Indo-China through trade, and may have reached Okinawa from one or more of these places simultaneously. In China it might have been known as the San-Ku-Chu.
