Ka (life force)

The Ancient Egyptians believed that a human soul was made up of five parts: the Ren, the Ba, the Ka, the Sheut, and the Ib. In addition to these components of the soul there was the human body (called the ha, occasionally a plural haw, meaning approximately sum of bodily parts).

The Ka (k3) was the Egyptian concept of life force, that which distinguishes the difference between a living and a dead person, death occurring when the ka left the body.

The ka often was represented in Egyptian iconography as a second image of the individual, leading earlier works to attempt to translate ka as double.

http://en.wikipedia.org/wiki/Egyptian_soul#cite_note-0