What does Omega mean?

Yes, but ABO is set in the United States and China.

Alpha male: The female part of the reproductive organs does not work or is born missing. The organs of the male part are larger than the normal standard, including the knot. Sociologically, because they are never pregnant, they have always been designated as soldiers or leaders. They also look superior to others.

Beta male: There are both male and female reproductive organs, both of which can play a role, but they rarely emit the smell of love and rarely enter estrus. They can enjoy sex without any burden, and they can mate at will without combination. They can get pregnant and start a family, but the fertility rate is not high. He is a good worker.

Omega male: having both male and female reproductive organs, with high reproductive rate and strong estrus, and will be distracted (usually alpha) before combining with others. Usually, they are busy with pregnancy and childbirth and are considered unfit for work. Is the rarest of all men.