You are confusing it with something esle. All living things have "life" in them. When they die, "life" leaves them, i.e. their "soul" separates; they stop breathing, they stop "living" and become dead. That goes for all living things. I know this is all Greek to you, and in fact it is Greek! :)
For us Romanists, I believe the parallel is spiritus (breath) from whence spirit:
1) The vital principle or animating force within living beings.
2) The soul, considered as departing from the body of a person at death.
3) Spirit, The Holy Spirit.
Which makes me also ponder that literally it would be the Father, Son and Holy Breath.