Answer:

For the majority of Christian denominations, the Holy Spirit, or Holy Ghost, is believed to be the third person of the Trinity,[2] a Triune God manifested as God the Father, God the Son, and God the Holy Spirit, each entity itself being God.[3][4][5] Nontrinitarian Christians, who reject the doctrine of the Trinity, differ significantly from mainstream Christianity in their beliefs about the Holy Spirit. In Christian theology, pneumatology refers to the study of the Holy Spirit