Gai'shain (Old Tongue: "those sworn to peace in battle") are Aiel who have been captured in a battle or raid. As part of their toh, they are required to wear white and serve their captors faithfully for a year and a day, touching no weapon and doing no violence. The only way to take such a prisoner is to touch a person without killing them while they are holding a weapon. After their time, they return to their clan as if nothing had happened.
It is far from unknown for Aiel taken gai'shain by an Aiel of the opposite sex to end up married to their captor.
Wise Ones, blacksmiths, children, and pregnant women or women with a child under the age of ten cannot be taken gai'shain. Exact "ownership" of the gai'shain is a variable matter; though each gai'shain swears only to one person, they can be and are often instructed to obey commands from other people as well.
While wearing the white, anything is possible. When Faile was gai'shain, she was told by Rolan that what happens while wearing white is forgotten when the white is taken off again. A wife can be taken to bed by the warrior who took her as gai'shain with no ji lost to either.