The Most Holy Trinity

Trinity Sunday is the first Sunday after Pentecost in the Western Christian liturgical calendar, and the Sunday of Pentecost in Eastern Christianity. Trinity Sunday celebrates the Christian doctrine of the Trinity, the three Persons of God: the Father, the Son and the Holy Spirit.

O Most Holy Trinity, Father, Son and Holy Spirit, I adore Thee profoundly. I offer Thee the most precious Body, Blood, Soul and Divinity of Jesus Christ present in all the tabernacles of the world, in reparation for the outrages, sacrileges and indifferences by which He is offended.

Like other Christians, Catholics believe in one God but we believe he exists in three parts or "persons". These are the Father, the Son and the Holy Spirit, know collectively as the Trinity. The three parts of God are referred to as:

• God the Father - the ultimate creator al all life. Christians believe that in the same way a parent cares for their child, God cares about his creation and wants to protect everything in it.
• God the Son also known as Jesus Christ - a key Christian belief is that God sent his only son Jesus to Earth as a sacrifice. Jesus' death made up for the sins of humans, and gave humans the chance for salvation and eternal life in Heaven. The resurrection and ascension of Jesus prove to Christians that he is the Son of God.
• God the Holy Spirit - the presence of God in the world, often represented as a dove. The Holy Spirit helps Christians to understand the idea that God is always present in the world, as stated in the Gospel of John: I will ask the Father, and he will give you another advocate to help you and be with you forever - the Spirit of truth (John 14:16-17). The Holy Spirit is considered to be a source of strength, courage and wisdom by many Christians.

Christians find the first mention of the Trinity in Genesis as part of the creation story, in which all three persons of the Trinity have a role. Belief in the Trinity is affirmed in the Nicene Creed, the statement of key religious beliefs that is often recited by worshipers during Christian ceremonies:

We believe in one God, the Father, the Almighty, maker of heaven and earth. We believe in One Lord, Jesus Christ, the only Son of God...of one Being with the Father, who as made man, he suffered death and he rose again. We believe in the Holy Spirit, the giver of life, who proceeds from the Father and the Son, who has spoken through the prophets.

When Catholics use the sign of the cross to bless themselves, they do so in the name of the Father, the Son and the Holy Spirit.

Some of the hymns that are sung at Mass mention the Trinity.

The Trinity is referred to during some of the Catholic sacraments, including baptism. The Gospel of Matthew describes the three person of the Trinity being present together at Jesus' own baptism.

"As soon as Jesus was baptised, he went up out of the water. At that moment heaven was opened, and he saw the Spirit of God descending like a dove and alighting on him. And a voice from heaven said, "This is my Son, whom I love; with him I am well pleased." (Matthew 3:16-17)

The term "Trinity" was first used in the 2nd century by Theophilus of Antioch, a convert to Christianity. However, Theophilus did not use the words "Father", "Son", or "Holy Spirit".

The First Council of Nicaea, formed in AD 325, was a group of bishops who were based in what is now Turkey. They confirmed the use of the term "Trinity", particularly regarding the ideas of God as Father and Son.

The First Council of Constantinople confirmed the nature and role of the Holy Spirit in AD 381.

This understanding of the Trinity as referring to God the Father, Son and Holy Spirit has continued to be a very important part of the Christian failth.