Body

Body (体) or Corpus (肉体) refers to the various vessels meant to house the Soul.

Astral Body
The Astral Body (星幽体) or Spirit Body (霊体) is the innermost body, the protective container for the soul. It also acts as a sort of computational device that translates the intention of the soul and relays it to the Spiritual Body. This layer requires a medium to preserve it, with it otherwise slowly dissolving back into the surrounding space and releasing the soul into the cycle of reincarnation.

Spiritual Body
The Spiritual Body (精神体) is what keeps the Astral Body and Soul protected from the environment. It acts as a foundation to accumulate power and a vessel to store energy.

For Physical Lifeforms and Demi-Physical Lifeforms it acts as a temporary virtual memory storage, while for Demi-Spiritual Lifeforms it acts as a thinking device and permanent memory storage similar to the brain. Most residents of Spiritual Worlds only have a Spiritual Body and lack a Material Body entirely.

Material Body
The Material Body (物質体) is the anchor that keeps the Spiritual Body attached to the physical plane and allows for the interaction with material objects.

Physical Lifeforms and Demi-Physical Lifeforms need a material body to stay alive, while Demi-Spiritual Lifeforms and Spiritual Lifeforms need one to remain anchored to the material world. Without a material body, beings of a spiritual nature are doomed to eventually either die or be rejected by the material world and ejected back into their spiritual world of origin.

Core
The Core (核) is an important part of the material body of beings like Monsters and similar. It serves as a vital function similar to that of a heart and if it's destroyed then the person in question will perish.

There are various different types depending on the nature of the being in question, including but not limited to; Magic Core (魔核), Chaos Core (聖魔核), Daemon Core (悪魔核), and Elemental Core (精霊核).

Magic Body
A Magic Body (魔体) is a temporary material body made of solidified Magicules, similar to the Body Double Extra Skill. It is typically used by Demi-Spiritual Lifeforms and Spiritual Lifeforms who do not have a proper material body to anchor them to the physical plane. It allows them to interact with the world and due to being made of essentially pure energy, can easily reform from any physical damage. It can also be used to "project" one's Spiritual Body to another location if their Material Body is immobile, such as in the case of the Dryads.

For beings of a spiritual nature that use a magic body as a medium for incarnation, it will be unstable and result in a constant loss of energy until it can no longer be maintained. Unless they are in an area with an extremely high level of magicule concentration—such as the Dungeon or the area near a Hell Gate—or are being supplied with a constant stream of energy from someone or something else, a Magic Body will typically only last for around a few days.