The 24th Greek letter is OMEGA (Ω), which is the last letter of the Greek alphabet. It is often used to represent the end of something, such as the end of a series or the conclusion of a task. In mathematics, it is used to denote the limit of a sequence or the greatest value in a set. In physics, it is used to represent the ohm, a unit of electrical resistance. In Christianity, it is used to symbolize the end of time and the second coming of Jesus Christ.