Date A Live: Terms
The term given when a Spirit returns to the other dimension which they came from. After which, further pursuit of them becomes impossible until they reappear.
|― as explained by Tamae-sensei a.k.a Tama-chan-sensei|
Reality: The Spirits that exist in the alternate dimension that is said to be the neighboring world and would occasionally appear into this world. On these occasions, there would be a large bend in the walls between the dimensions, causing a phenomenon known as a spacequake to occur. Whether it was on a large or small scale– the area where the Spirits would appear would be absurdly destroyed, as though a bomb had exploded. 
A sphere of influence created by a wizard's CR-unit or a Spirit's Mana. The artificial Territory created using the said technology is produced by a device called Realizer. It can give advantages to an ordinary human. When a human Wizard is inside his/her Territory, he/she may be capable of doing the following feats:
- Fly or levitate one's body.
- Create barriers for protection against attacks.
- Levitate other objects regardless of their weight.
- Strengthen the body of a human.
- Increase the attack and defensive power of weapons like guns, laser swords, and missiles.
- Trap someone or something inside another Territory.
Inside a Territory, a Wizard is said to be capable of doing magic. Ellen Mira Mathers' Territory is famous for being able to materialize without the help of a CR-Unit. Artemisia Bell Ashcroft's Territory is also unique for being able to extend its sphere at an incredible length.
Eurasia Sky Disaster
Eurasia Sky Disaster (ユーラシア大空災) is the original spacequake 30 years ago that occurred off the frontier between China and Mongolia, killing over 150 million people and starting a chain of similar disasters around the world that would last approximately six months. Supposedly, it was caused by Westcott, Ellen, and Elliot's attempt to summon the First Spirit.
People who are trained and equipped with Realizers to fight Spirits.
Spirits are extraterrestrial beings from a different dimension who's arrival is usually preceded by a spacequake. Each Spirit possesses an Astral Dress as well as an Angel, however, their abilities are unique. Each Spirit displays different levels of knowledge about Earth.
Reiryoku (霊力, lit., Spiritual Power) is an energy that fuels the attacks of each Spirit. Each Spirit is ranked differently in regards to how much Reiryoku they possess.
Maryoku (魔力, lit., Magical Power) is the energy released by Wizards when they use attacks channeled by the Realizer.
Date A Bullet: Terms
Neighboring World (隣界, Tonarikai) is an alternate dimension where Spirits exist before arriving at the real world. The Neighboring World is composed of ten different regions named after the Sephirot of the Tree of Life in Kabbalah. Each region is connected to one of the ten Spirits, which is determined by their Spirit number.
Quasi-Spirits (準精霊, Jun Seirei) are beings that live in the Neighboring World after the Spirits left for the real world. Unlike a normal Spirit, they only possess a fragment of a Sephira Crystal.
The Neighboring World is composed of ten different regions named after the Sephirot of the Tree of Life in Kabbalah. Each region is connected to one of the ten Spirits, which is determined by their Spirit number.
Dominions are the current rulers of the Neighboring World. Following the departure of the Spirits from the Neighboring World, each of the ten regions of the Neighboring World came to be under the rule of a Quasi-Spirit. As the leader, the Dominion stands on the top of the hierarchy of the region and determines how Sephira fragments are distributed in that region. Dominions also take charge in emergency situations in conjunction with ruling over their region, which includes upholding societal values and keeping everything running smoothly.
- One male Wizard is noted to have fought Shido in Volume 7, named as Andrew Carthy, and was swiftly dispatched.
- Kyouhei Kannazuki is stated to have once been a wizard, but has never been shown as one.
- So far in Date A Live story, Kurumi, Kotori, and Miku have shown the ability to summon spacequakes at will.
- Kotori mentioned that a Spacequake can be stopped by another Spacequake if they are triggered at the same time with the same magnitude.
- The largest spacequake was created by The First Spirit 30 years before the beginning of the events in Date A Live.