Triquetra & Trinity knot

The iconic Triquetra (or Trinity knot) is the most common kind of Celtic knot and has a myriad of symbolic interpretations. With one continuous line interweaving around itself, it symbolizes the eternal spiritual life as well as unity.
Pagans cherish it as a representation of the forces of Nature, earth, fire and water and it was latterly adapted by Christians to represent the three elements of the holy Trinity.