Trinity
Latin trinitas, "threeness"; first used in Latin by Tertullian (c. 200)
Definition
The central Christian mystery of one God in three divine Persons: Father, Son and Holy Spirit.
The Persons are really distinct, yet each is wholly God; they share one divine nature (CCC 253-255). The doctrine was articulated against heresies at the Councils of Nicaea (325) and Constantinople (381).