For the majority of Christian denominations, the Holy Spirit or Holy Ghost is the third person (hypostasis) of the Trinity: the Triune God manifested as God the Father, God the Son, and the Holy Spirit; each person itself being God. Some Christian theologians identify the Holy Spirit with the Ruach Hakodesh in Jewish scripture, and with many similar names including the Ruach Elohim (Spirit of God), Ruach YHWH (Spirit of Yahweh), and the Ruach Hakmah (Spirit of Wisdom). In the New Testament it is identified with the Spirit of Christ, the Spirit of Truth, the Paraclete and the Holy Spirit.
The New Testament details a close relationship between the Holy Spirit and Jesus during his earthly life and ministry. The Gospels of Matthew and Luke and the Nicene Creed state that Jesus was “conceived by the Holy Spirit, born of the Virgin Mary”. The Holy Spirit descended on Jesus like a dove during his baptism, and in his Farewell Discourse after the Last Supper Jesus promised to send the Holy Spirit to his disciples after his departure.
The Holy Spirit is referred to as “the Lord, the Giver of Life” in the Nicene Creed, which summarises several key beliefs held by many Christian denominations. The participation of the Holy Spirit in the tripartite nature of conversion is apparent in Jesus’ final post-resurrection instruction to his disciples at the end of the Gospel of Matthew (28:19): “make disciples of all the nations, baptizing them into the name of the Father and of the Son and of the Holy Spirit,” and “For where two or three are gathered together in my name, there am I in the midst of them.” Since the first century, Christians have also called upon God with the trinitarian formula “Father, Son and Holy Spirit” in prayer, absolution and benediction. In the book of the Acts of the Apostles the arrival of the Holy Spirit, happens fifty days after the resurrection of the Christ, and is currently celebrated in Christendom with the feast of Pentecost.
In Christian theology, pneumatology refers to the study of the Holy Spirit.