Omega (Ω, ω) is the 24th and last letter of the Greek alphabet. In Classical Greek, it represented the vowel sound [ɔː], which later became [o] in Modern Greek. In the Greek numeral system, it has a value of 800.
The word "omega" comes from the Greek ὦ μέγα (ō méga), meaning "great O", in contrast to ὂ μικρόν (o mikrón), "small O", the name for the letter omicron (Ο, ο). The word "omega" is used in various contexts to signify the end or the last in a series.