A Spirit (幽霊, Yuurei) is a deceased entity in which is still active. They're the very soul of an dead individual.
A Spirit is usually created after the death of an individual in which their bodies disintegrate, damage, or their soul is simply out of their bodies. Spirits retain their appearance at the time of their death (including any bodily causes of death) and even their personality. As such, they're generally more friendly despite their perceived notions of malice to the general populace. Spirits may also be created by a Necromancer using the Book of the Dead, though resurrects individuals as Evil Spirits.
Evil Spirits (悪霊, Akuyō), like ordinary Spirits, are deceased entities in which have became active, usually as the result of some Magic or otherwise. They're much more powerful, retaining physical bodies and powers they may of even had prior to their death. As their names suggest, they're also evil in nature.
List of Spirits
Main article: Category:Spirit