In Christian doctrine, the unity of the Father, Son, and Holy Spirit as one God in three persons.
The word Trinity does not appear in the Bible. It is a doctrine formulated in the early church to interpret the way God revealed himself, first to Israel, then in Jesus as Saviour, and finally as Holy Spirit, preserver of the church. The doctrine of the Trinity developed in the early centuries of the church and was explicitly stated at the Council of Nicaea in 325.