This is clear from the fact that we commonly speak of “yielding up the spirit” when someone dies. In this sense, then, “spirit” means the life of our breathing. In fact, the word “spirit” is derived from [a word for] breathing, which is why in Hebrew the word that means “spirit” also means “wind.”
We have two inner springs of life. One is the motion of the heart, and the other is the breathing of the lungs. The life that depends on the breathing of the lungs is the one properly meant by “spirit” and also by “soul.” In the appropriate place there will be a description of the way this is coordinated with our cognitive thinking, while the life dependent on the motion of the heart is coordinated with the love associated with our will.
It is clear from the following passages that “spirit” in the Word refers to an individual’s life.
You gather in their spirit; they breathe their last and return to dust. (Psalms 104:29)
He remembered that they were flesh, a spirit that departs and does not return. (Psalms 78:39)
When their spirit leaves, they will return to the earth. (Psalms 146:4)
Hezekiah expressed grief that “the life of his spirit” was departing. (Isaiah 38:16)
The spirit of Jacob came back to life. (Genesis 45:27)
A molded image is a lie, and there is no spirit within it. (Jeremiah 51:17)
The Lord Jehovih said to the dry bones, “I will put spirit into you so that you will live. Come from the four winds, O spirit, and breathe on these people who have been killed, and they will live”; and the spirit came into them, and they came back to life. (Ezekiel 37:5, 6, 9, 10)
When Jesus took the daughter’s hand, her spirit returned, and she arose immediately. (Luke 8:54, 55)
from The Lord, Section 47