Demai (“Produce from One Who is Suspected to Have Neglected Tithing”) is a tractate in Seder Zeraim (“Order of Seeds”) that discusses the concept of “demai” and how to tithe it. Its seven chapters address details such as which fruits are exempt from the laws of demai, situations in which it is permissible to eat demai without tithing, and guidelines for determining whether an unknown person can be trusted to have tithed.