Overview:
This work is currently set in an "omegaverse" setting. An omegaverse world is an alternate universe with defined biological roles based on a hierarchical system. People are divided into two sexes instead of one: a primary sex (male or female) and a secondary sex (Alpha, Omega, Beta, etc.,). Though the primary sex constitutes for a large portion of the individual's reproductive anatomy, the secondary sex will modify and emphasize a particular demeanour within the individual's reproductive physiology. Each author has differences when it comes to their own omegaverse setting so please do keep that in mind.
Genders:
Geneias: Geneias are the highest rank in the dominance hierarchy, making up roughly 0.0001% of the global population(which is roughly ~7000 people). Seeing a Geneia is really rare. They have the normal anatomy and traits of an Alpha. One key difference between them is that they have stronger pheromones than any of the secondary genders. They are able to make Alphas submit to their pheromones easily. Another key difference is that they are usually much stronger and athletically more capable than Alphas. Lastly, they can impregnate any secondary genders, even Alphas regardless of their primary gender. If a person is impregnated by a Geneia, they usually exhibit Omega-like symptoms.
Geneias are often misgendered as they present as an Alpha. It is not until maturity (around the age of 18 to 20) when their pheromones become stronger and exhibit signs of change. There have been Geneias, however, that have had a strong pheromone since presenting.
Alphas: Alphas are the second highest rank in the dominance hierarchy and make up around 15% of the population. They exhibit "dominant" behaviour or have other temperamental quirks. They are able to impregnate Omegas no matter the gender of the alpha. Male Alphas usually have a knot when aroused. However, their female counterpart does not. Instead, they have retractable members. Female alphas also cannot get pregnant except under special circumstances. Alphas usually have a strong scent and can induce heats in omegas.
Betas: Betas are subordinates to Alphas in the dominance hierarchy, making up roughly 75% of the global population. Betas are often presented as having "normal" human anatomy, with none of the special attributes of the Geneias, Alphas and Omegas. Male Betas can impregnate Omegas while female Betas can be impregnated by Alphas. Lastly, Betas can sense pheromones but are cannot be induced to a heat.
Omegas: Omega's are the lowest rank in the dominance hierarchy that make up around 10% of the population. They can get pregnant and go into heat. Male Omegas are self-lubricating an have the ability to become pregnant. Omegas are often portrayed as beautiful and fragile, with frailer bodies than all of the other secondary genders (but that is not always the case). It is very rare to see Omega's working in physical-heavy jobs.
Female Omegas have higher fertility than their Beta counterparts but otherwise have the same anatomy. Male Omegas on the other hand paint a different story. Males lack reproductive organs that females have. Therefore, it's supplemented by using the anal cavity, serving as both the natural processed like waste removal and the uterus.
Terminology:
Presenting: Presenting is when an individual develops and reveals their secondary gender—Geneia, Alpha, Beta or Omega. Usually, a person presents around puberty or adolescence (around the age of 14). Individuals are tested at the age of 6 for their secondary gender.
Priming: The stage (usually around ages 4-6) where the glands mature rapidly.
Scents/Pheromones: All secondary genders give off a very specific sort of scent as a personal marker to their primary and secondary sex. They all have the ability to "scent" others, which is simply the process of spreading their specific scent on another person or object.
Scent Glands: Areas on the body (predominantly the neck) that release pheromones unique to each individual. These scents help communicate the mood, rank, and attraction.
Heats: A heat/estrus is a period of 3-5 days where an Omega-identified or Geneia marked individual will experience excitability and have an increase in fertility. This comes in tandem with a large release of pheromones to communicate the biological shift to others.
Nest: A nest is a structure that an Omega identified or Geneia marked individuals build during heat and while pregnant. It can vary in appearance, but serves as a calming purpose to help one without their partner.
Ruts: A period of 3-5 days where an Alpha or Geneia individual will act more possessive and territorial than normal. It doesn't not specify ties to the need with mating (although it usually is). Normally rutting periods are more common after being mated, as a part of a biological cycle to protect and impregnate said mate. Rutting periods in Alphas and Geneias typically happen 2-3 times a year.
Knotting: A bulge of muscles at the base of an Alpha/Geneia's member that swells either when erect or before an orgasm, often to keep both individuals from separating during and after ejaculation to ensure conception. A knot will last anywhere between 30 minutes to 1 hour.
Marking: Marking is when an individual imprints their scent onto another person, often as a sign of claim or protection. It can also be done to calm a partner. Marking can be done in different ways:
Temporary Marking: Done by lightly piercing the scent gland and injecting their pheromones. This mixes the two pheromones of the individual together which lasts several months depending on the individual's compatibility with one another.
Bonding: Bonding is the most intense form of marking, creating a permanent link between two people. This is done through biting the scent gland whilst in a heat or rut. Bonding ties mates together so strongly that they can sometimes sense each other's emotions. Unbonding can be extremely painful as well and can even cause death in extreme cases.
Slick: A word describing the self-lubrication that an Omega or Geneia marked individual has/experiences, especially during their heat.
Suppressants: Medication given to Geneias, Alphas, or Omegas to suppress their rut or heat cycles. It can also suppress the fertility of individuals and is a type of "birth control". Using suppressants often can greatly disrupt one's body and cause chemical imbalances.
Scent Blockers/Patches: Spray or patches that mask an individual's scent.
This information was compiled from multiple different sources. Special thanks to @DarthSuki on AO3 and @Velvelyami on Wattpad as most of the information above is from them!
https://www.wattpad.com/546924059-the-unofficial-guide-to-the-omegaverse-basic
https://archiveofourown.org/works/8240798/chapters/18885730#workskin