Man is spirit. This means that his essence is spirit. This is simply because he originated from the spiritual realm. When he enters material Creation, however, he is forced to cover himself with the essence of whatever region he finds himself. The human spirit with his coverings in material Creation without the physical body is referred to as a human soul.
Therefore, the human being after it has dropped its physical body is referred to as a soul, which is a combination of spirit which is the core and the various finer coverings around this spirit.