Triquetra (/traɪˈkwɛtrə/; Latin tri- "three" and quetrus "cornered") originally meant "triangle" and was used to refer to various three-cornered shapes. Nowadays, it has come to refer exclusively to a particular more complicated shape formed of three vesicae piscis, sometimes with an added circle in or around it. Also known as a "trinity knot," the design is used as a religious symbol by both Christians and polytheists. Christians use the triquetra to represent the Trinity of the Father, Son, and Holy Spirit: three distinct persons of one divine essence.
The triquetra has been found on runestones in Northern Europe and on early Germanic coins. It presumably had pagan religious meaning and it bears a resemblance to the Valknut, a symbol associated with Odin.
The triquetra is often found in Insular art, most notably metal work and in illuminated manuscripts like the Book of Kells. It is also found in similar artwork on Celtic crosses and slabs from the early Christian period. The fact that the triquetra rarely stood alone in medieval Celtic art has cast reasonable doubt on its use as a primary symbol of belief. In manuscripts it was used primarily as a space filler or ornament in much more complex compositions, and in knotwork panels it is a design motif integrated with other design elements. Celtic art lives on as both a living folk art tradition and through several revivals. This widely recognized knot has been used as a singular symbol for the past two centuries by Celtic Christians, Pagans and agnostics as a sign of special things and persons that are threefold.
The symbol has been used by Christians as a sign of the Blessed Trinity (Father, Son and Holy Spirit), especially since the Celtic Revival of the 19th century. When modern designers began to display the triquetra as a stand-alone design, it recalled the three-leafed shamrock which was similarly offered as a Trinity symbol by Saint Patrick. Some have also suggested that the triquetra has a similarity to the Christian Ιχθυς symbol. The triquetra has been used extensively on Christian sculpture, vestments, book arts and stained glass. It has been used on the title page and binding of some editions of the New King James Version.
A very common representation of the symbol is with a circle that goes through the three interconnected loops of the Triquetra. The circle emphasizes the unity of the whole combination of the three elements. It is also said to symbolize God's love around the Holy Trinity.
In contemporary Ireland, it is traditional for a man to give a loved one a trinket such as a necklace or ring signifying his affection towards her. The triquetra, also known as a "trinity knot," is believed to represent the three promises of a relationship such as to love, honour, and protect, and can be found as a design element on Claddaghs and other wedding or engagement rings.
The triquetra design on the cover of a replica of the Book of Shadows central to the television series Charmed.
It is difficult to date the exact origin of the Celtic triquetra, and whether it was first used in a Christian or pagan context; the distinctive interlace/knotwork artistic style did not fully develop until ca. the 7th century A.D., but the triquetra is the simplest possible knot. Modern Pagans use the triquetra to symbolize a variety of concepts and mythological figures.
Due to its presence in insular Celtic art, Celtic Reconstructionists use the triquetra either to represent one of the various triplicities in their cosmology and theology (such as the tripartite division of the world into the realms of Land, Sea and Sky), or as a symbol of one of the specific triple Goddesses, for example, The Morrígan.
Germanic Neopagan groups who use the triquetra to symbolize their faith generally believe it is originally of Norse and Germanic origins.
The band Payable on Death (P.O.D.) uses this symbol on most of their CD covers.
The triquetra is part of The Script's symbol of "Science and Faith".
In recent years, the symbol has become well-known due to its use on the cover of the Book of Shadows used by the three Halliwell sisters on the American TV show Charmed. It represents the three sister witches' working together as one, and is intact when the "power of three" is intact and separated when the "power of three" is divided.
The Vampire Diaries Season 5.07 - Death and the Maiden used the triquetra when Tessa had all three dopplegangers together and was trying to change the Anchor from Amara to Bonnie.
The triquetra is used in the fourth season of the TV series Falling Skies, where it is worn on a necklace by the residents of Chinatown. A much larger triquetra decorates the wall of a shrine in Chinatown. It is explained that the symbol represents unity, a core value among the members of the community, who wilfully decide not to fight the Espheni.
Topologically, the interlaced form of the plain triquetra is a trefoil knot.
Gallery of variant forms
Triquetra composed exactly of three overlapping Vesica piscis symbols.
An interlaced double Triquetra.
Tightly-knotted form of triquetra.
Triquetra interlaced with circle as Christian Trinitarian symbol (a "Trinity knot").
Triquetra in blue as part of an interlaced Christian Trinitarian decorative symbol.