1. The soul or vital spirit; the creative force of a person.
2. In theology, the Spirit of God; the Holy Ghost.
3. The life-giving principle.

According to the school of medicine in ancient Alexandria, life was associated with a vapor called the pneuma.

The belief in pneuma was called pneumatism. In hindsight, pneumatism was an early attempt to explain respiration, or breathing; which is, indeed, the "life-giving principle".

4. Etymology: from Greek pneuma, "breath, wind, air" or "that which is breathed" or "blown"; from pnein, "to blow"; which is considered to be from an imitative origin.