Holy Spirit. For the majority of Christian denominations, the Holy Spirit, or Holy Ghost, is the third person of the Trinity: the Triune God manifested as God the Father, God the Son, and God the Holy Spirit; each entity itself being God. 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. Due to Christianity's historical relationship with Judaism, theologians often identify the Holy Spirit with the concept of the Ruach Hakodesh in Jewish scripture, in the belief Jesus was expanding upon these Jewish concepts. Similar names, and ideas, include the Ruach Elohim, Ruach YHWH, and the Ruach Hakmah. 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: 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 celebrated in Christendom with the feast of Pentecost. The Koine Greek word pneûma is found around 385 times in the New Testament, with some scholars differing by three to nine occurrences. Pneuma appears 105 times in the four canonical gospels, 69 times in the Acts of the Apostles, 161 times in the Pauline epistles, and 50 times elsewhere. These usages vary: in 133 cases, it refers to spirit in a general sense and in 153 cases to spiritual. Around 93 times, the reference to the Holy Spirit, sometimes under the name pneuma and sometimes explicitly as the pneûma tò Hagion. It was generally translated into the Vulgate as Spiritus and Spiritus Sanctus. The English terms Holy Ghost and Holy Spirit are complete synonyms: one derives from the Old English gast and the other from the Latin loanword spiritus. Like pneuma, they both refer to the breath, to its animating power, and to the soul. The Old English term is shared by all other Germanic languages and is older, but the King James Bible used both interchangeably, and 20th-century translations of the Bible overwhelmingly prefer Holy Spirit, probably because the general English term ghost has increasingly come to refer only to the spirit of a dead person.