Holy Ghost; the healing creational energy at the source of everything there was, everything there is, and everything there is to be, and (hence) everything there is to know.
This energy is the emanation of God himself, who is above everything and - since every conscious being is provided with free will, leaving all options open, if it had to be captured in one word,- Love would be the best description for it.
Our material universe or the Cosmos is maintained by this energy which can be seen as an invisible Sun at the center on a large scale, but also at the same time, as the source of every atom and every "particle" on the smallest scale. In the sense that this universe is separated from "the others", this Light source in the middle; the entity that is the god of this universe, may be called the Son of God, but in reality of course it is the same energy, the same Spirit as God Himself who may be called the Father. In fact; the Father and the Son are one and so is the Spirit that emanates from them.
The original Sumerian word for ghost or spirit is An, or Anu. The Hebrew word An still stands for power, energy and can also mean son.