Omega (uppercase/lowercase Ω ω), is the 24th and last letter of the Greek alphabet. It stood for a long "o" sound in Ancient Greek. It still stands for "o" in Modern Greek, but there is no longer a difference between long and short vowels, so it sounds the same as Omicron. In the system of Greek numerals, it stands for the number 800.
In electromagnetism and engineering, uppercase omega (Ω) is used as the symbol for ohms, which are the units of electrical resistance. In physics and other sciences, lowercase omega (ω) is often used to represent angular frequency.
In modern English the phrase "From alpha to omega" expresses the idea of "everything".