The world of Rachel Morgan has a lot of specialized jargon and slang, which gives the books character, but may add complexity for the uninitiated.
Brimstone: An illegal drug. Can be baked into cookies without losing potency. While outlawed by humans for its ability to make people high, it is an effective metabolism-boosting medicine. Coveted by vampires to help their shadows recover from blood loss.
Brimstone, medical-grade: Brimstone that is refined enough to remove the impurities that abusers covet for the "high", as well as dangerous toxins. Costs a thousand dollars per ounce, supplied in Cincinnati exclusively by Kalamack Industries.
Circle: A spherical or oblong barrier of ever-after, produced by ley-line magic. A circle always has a circular cross-section through the ground, takes the color of the caster's aura, and is somewhat bright and translucent. Circles vary in strength, depending on the power in them and the way they were made. Circles drawn on the ground with magnetic chalk, metal, salt, blood, or cremation ash prior to invocation are stronger than undrawn circles, and can be layered concentrically. Undrawn circles always center on the caster and only one at a time can be maintained. Circles can be used to hold people in or keep things out.
Ever-After: A reality that parallels Earth, connected by ley lines, where demons reside. The sun is toxic and only lesser, animalistic demons live on the surface world during the day; demons live underground.
FIB: The Federal Inderlander Beaureau.
The Hollows: The region of the Cincinnati Metro south of the Ohio river, which looks just like a Human suburb, but where the larger concentration of Inderlanders live.
I.S.: Inderlander Security.
Inderlander: Any sentient species that isn't human (any supernatural creatures).
Ley line: A linear font of magical energy, possibly part of life itself. Many were produced when demons flew from the ever-after and landed in reality, and they can be found all over the planet, though they can "dry up" and extinguish. Act as links between reality and the ever-after.
Living vampire: The offspring of an undead vampire and a human. Since they already have the vampire virus included in their DNA (in provirus form), they automatically turn into undead vampires when they die. They otherwise seem human, except for certain physical advantages, fangs, and a great desire for blood and trust. See Inderland Races.
Pix: The act of a pixy shedding offensive pixy dust from his or her wings onto a target with the intent to harm. Causes severe itching and red rashes where it hits.
Run: an attempt to catch a criminal; a raid; a field operation in law enforcement.
Shadow: A vampire's playmate, of any race, who has given up their will to the vampire and in turn regularly gives and receives blood from them. An exclusive relationship. Often acquiring one while living, vampires depend on their shadow to be their steady source of blood when they are in the undead state.
Splat ball: Small paint-ball like pellets that hold spell potions, designed to break open on impact and spell the target. Have an expiration date based on the shelf life of the invoked potion--usually less than a week.
Splat gun: Paint-ball pistols that can hold and shoot splat balls, propelled by air.
Sticky silk: A thick spray-polymer that traps pixies. Pixies can work their way out of it, but are vulnerable while trapped.
The Turn: A period in the 1950s and '60s where a sizable chunk of the human population was wiped out by a human-made virus carried in tomatoes. Only humans and descendants of humans with human genes were affected by the virus. Inderlanders revealed themselves to humans at this time, creating the precarious societal balance that exists in Rachel Morgan's era, the early 2000s.
Tag: successful apprehension of a target, e.g. arresting a criminal.