Holy Spirit or Holy Ghost [ghost, i.e., spirit, a translation of Gr. pneuma=breath, air], in Christian doctrine, the third person of the Trinity. The Holy Spirit is sometimes defined as the aspect of God immanent in this world, in human beings, and in the church. Jesus' promise to his disciples of a Comforter (or Paraclete, i.e., advocate), in John 14, is considered his principal reference to the Holy Spirit, and the descent of the Holy Spirit on the apostles and the communication of the gift of tongues, as recounted in Acts 2, is thought to be an example of the work of the Holy Spirit in time. This incident is commemorated on Pentecost (Whitsunday). Certain Christian groups, such as the Montanists and the Society of Friends, have attributed utterances of their members to the inspiration of the Holy Spirit. The dove is the symbol of the Holy Spirit. For the controversy over the procession of the Holy Spirit, see creed.