Soul
Every living being in Neon Genesis Evangelion has a soul (魂, tamashii). The soul is everything that makes up a living thing's being. Souls in NGE originate from the Chamber of Guf, and enter & leave through the Doors of Guf. Souls then combine with a an appropriate vessel in order to create life.
This article bears the unpleasant designation of "Stub." This is a Bad Thing. Provide a great service to NGE fan-geeks everywhere by making it awesomer!