Yoma: Monsters/demons that prey on humans. They eat the entrails of humans and devour their brains in order to assume the identity of the victim. Only Claymore and other yoma are able to sense them.
The Organization: A mysterious group that creates and dispatches Claymore to one of 47 regions. They require a fee for this.
Black Coats/Man in Black: Dispatchers from the Organization that serve as keepers for the Claymore. A Claymore does not take the money she earns herself; instead the money is given to one of the black cloaks and given to warriors as a stipend.
Yoki: Otherwise known as "yoma" energy, any given amount of otherwordly energy a yoma, Awakened Being, or Claymore releases or uses.
"Voracious eater": The public's term for an Awakened Being.
Awakened Being: When a Claymore reaches his or her limit in battle, they can no longer contain their demonic yoma energy and transform into a monstrous creature far beyond a normal yoma. These beasts are called Awakened Beings. Because of this happening commonly among male Claymore, only female Claymore are created.
Abyssal One: In the history of the Organization, there have been three instances where a Claymore ranked number 1 has awakened--one in the generation of male warriors, and two in the generation of female warriors. Once, an Awakening of a number 1 nearly led the Organization to the brink of ruin. These old, powerful beings are known as Dwellers of the Deep, the Three Powers, or Abyssal Ones. Excluding the ruined east, one of the Three Powers resides in each region: Isley of the North, Luciela of the South, and Riful of the West. They are so powerful that the Organization leaves them to their own devices, and Claymore avoid them at all costs.