The Trinity can be a very difficult concept to teach to children, but there are a variety of analogies that can be used. Even full-grown adults have had great difficulty understanding the Trinity, and it will always remain one of the greatest (if not THE greatest) mysteries of our faith. How can there be three Persons, but only one God? How can we believe that God is a Trinity, that He is Father, Son, and Holy Spirit, but still claim to believe in only one God? How is it that there are three Persons, but not three gods? How can the Father, Son, and Spirit be distinct figures with unique roles in salvation history, but not separate entities? And how can we explain this to our students when we don’t fully understand the Trinity ourselves? You can take a look at the reflection associated with Chapter 4’s prayer service for a fuller exploration of the nature of the Trinity.
Children are not the only ones who have needed some sort of symbol to better understand the Trinity. Centuries ago, St. Patrick used the shamrock to explain the Trinity to the people of Ireland. They had never heard of the Trinity, and could not understand how there could be three Persons in one God, rather than three gods, and so St. Patrick devised a way to explain this mystery to them. Every shamrock has three distinct leaves, but they are all part of the shamrock. This simple explanation won an entire nation to Christ.
There are many different forms of the shamrock activity. You can use a coloring page to teach this lesson, or something more elaborate such as the project shown above. In the shamrock activity depicted above, the names of the three Persons of the Trinity were paired with symbols for each (a church for the Father, a cross for the Son, and a dove for the Holy Spirit) and attached to a pre-cut shamrock. There is also a little explanation that can be attached to the back of the shamrock that reads, “Just like the leaves on each shamrock I see, there are three parts to the Holy Trinity. First is God the Father, then Jesus, His only Son, and the Holy Spirit together as One.”
The above activity can be found in our resource room, and a limited supply is available for use by our catechists.
Coloring pages of the shamrock for explaining the Trinity can also be found here.
Religious Education Resources 
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