- The term "triquetra" has formerly also been used to refer to the triple spiral design discussed under triskelion.
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It is used as an ornamental design in architecture, and in medieval manuscript illumination (particularly in the Insular tradition). Its depiction as interlaced is common in Insular ornaments from about the 7th century. In this interpretation, the triquetra represents the topologically simplest possible knot.
The term triquetra in archaeology is used of any figure consisting of three arcs, including pinwheel[disambiguation needed] design of the type of the triskeles. Such symbols become frequent from about the 4th century BC ornamented ceramics of Anatolia and Persia, and it appears on early Lycian coins.
The triquetra is found on runestones in Northern Europe and on early Germanic coins. It bears a resemblance to the so-called valknut, a design of three interlacing triangles, found in the same context.
The triquetra is often found in insular art, most notably metal work and in illuminated manuscripts like the Book of Kells. It is a "minor though recurring theme" in the secondary phase of Anglo-Saxon sceatta production (c. 710–760). It is found in similar artwork on early Christian High Crosses and slabs. An example from early medieval stonework is the Anglo-Saxon frith stool at Hexham Abbey.
The symbol has been interpreted as representing the Christian Trinity, especially since the Celtic revival of the 19th century. The original intention by the early medieval artists is unknown and experts warn against over-interpretation.
The triquetra has been a known symbol in Japan called Musubi Mitsugashiwa. Being one of the forms of the Aryan Iakšaku dynasty signs, it reached Japan with the dynasty's Kāśyapīya spreading technology and Buddhism via Kingdom of Khotan, China and Korea.
The triquetra is often used artistically as a design element when Celtic knotwork is used, especially in association with the modern Celtic Nations. The triquetra, also known as a "trinity knot", is often found as a design element is popular Irish jewelry such as claddaghs and other wedding or engagement rings.[page needed]
Celtic pagans or neopagans who are not of a Celtic cultural orientation, may use the triquetra to symbolise 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 Celtic triple goddesses, for example the battle goddess, The Morrígan. The symbol is also sometimes used by Wiccans and some New Agers to symbolise the Triple Goddess, or as a protective symbol.
In the German Netflix series Dark (2017), it symbolizes the caves closed time loops with each year being 33 years apart, with the past affecting the future and the future influencing the past. The Triquetra is of significant symbolic value to the time travelers. This symbol can be seen on the Cave's metal door, on the Emerald Tablet, in The Stranger's papers and in the Sic Mundus photo. 
Close-up of a triquetra on one of the Funbo Runestones.
Interlaced triquetra on a Norwegian penny minted under Harald Hardrada (r. 1047-1066)
- Variant forms
Triquetra composed exactly of three overlapping Vesica piscis symbols.
The cross of triquetras, or "Carolingian cross".
Celtic cross with triquetras.
- H. Trætteberg, E. Moltke, I. Lindeberg, "Triquetra" in: Kulturhistorisk leksikon for nordisk middelalder, vol. 18 (1982), p. 634–6356.
- Martin Blindheim: Graffiti in Norwegian stave churches c. 1150 – c. 1350, Oslo 1985, i.a. p. 44–45
- John Burley Waring, Ceramic Art in Remote Ages (1874), 84f.
- Tony Abramson (ed.), Two Decades of Discovery Studies in Medieval Coinage 1, Boydell Press (2008), p. 1.
- "The Corpus of Anglo-Saxon Stone Sculpture". www.ascorpus.ac.uk. Retrieved 16 July 2019.
- McMahon, Seán (1999). Story of the Claddagh Ring. Mercier Press. ISBN 9781856351898.
- Mac Mathúna, Liam (1999) "Irish Perceptions of the Cosmos" Celtica vol. 23 (1999), pp.174–187
- Cunningham, Scott (2004) , "Rune Magic", Wicca: A Guide to the Solitary Practitioner, Woodbury, MN, U.S.A.: Llewellyn, p. 191, ISBN 978-0-87542-118-6.
- Ross, Dalton; Snetiker, Marc (17 November 2013). "Michonne's Katana". Entertainment Weekly. Retrieved 30 October 2016.
- Keveney, Bill (12 October 2014). "'The Walking Dead,' up close and personal". USA Today. Retrieved 30 October 2016.
We put a trinity on there – mind, body, soul. That's important to who Michonne (Danai Gurira) is. We put some squares around it. And (executive producer) Robert Kirkman wanted a symbol that was like the biohazard symbol … so we put a triple goddess on there, which looks exactly like it.
- "Triquetra | Official DARK-Guide Season 1&2 | NETFLIX". DARKNetflix. Retrieved 30 May 2020.