What is a Trefoil?

Jessica Ellis
Jessica Ellis

In religious art, graphic design, and the natural world, the trefoil is a commonly seen shape. The word comes from a Latin term that translates roughly as three-leaved. Certain plants are known to often sprout in a trifoliate pattern, including certain species of clover, birdsfoot, and poison oak. Over time, the unique three-leaf pattern has become greatly symbolic, and is often found in religious and heraldic motifs.

The Irish clover leaf is a trefoil.
The Irish clover leaf is a trefoil.

Many people know the three-leaf symbol as a warning sign of danger. The poison oak and poison ivy plants, found in temperate regions, feature a three-leafed design made famous by the common saying, “Leaves of three, let them be.” These plants are known to cause an itchy rash that can last for days after contact, making the trifoliate menace important to avoid while traveling in woody areas.

The recycling logo uses the trefoil symbol.
The recycling logo uses the trefoil symbol.

Clover or shamrocks are often depicted as trefoliate when used in the national symbolism of Ireland. Throughout the country, they are used as an identifying emblem, prominently found on the sports team paraphernalia and even painted on the airplanes of the Irish airplane giant, Aer Lingus. Some believe that the association of the trefoil shamrock with Ireland dates back to the days of St. Patrick, who, according to legend, brought Christianity to Ireland. In some parts of the world, Irish ancestry is celebrated by wearing a shamrock on 17 March, also known as St. Patrick’s Day.

The shape is an apt emblem of Christianity throughout the world, as it is often used to visually represent the holy trinity of God the Father, Jesus, and the Holy Spirit. The patterns are often found in cathedral and church architecture, both as carved symbols and sometimes as windows. It is prominently found in Christian structures built during the age of Gothic architecture, mostly between the 12th to the 16th centuries.

The trefoil also appears as heraldic imagery, cropping up quite frequently in coats of arms and family symbols. In addition to displaying Irish ancestry or a connection to Ireland, the symbol can also stand for perpetuity. In many Girl Scout and Girl Guide troops, it is representative of a three-part promise made by members.

The Girl Scout use of the design is only one example of the many modern symbols that make use of this ancient motif. Looking closely at the symbols for recycling, bio-hazards, or radioactivity, the influence of the three-leaved image is evident. In many different forms of symbolism, three is considered a powerful number; it is significant not only to Christianity, but also to Buddhism, Hinduism, Platonic philosophy, and even the practice of Wicca. As a visual representation of the powerful three, the trefoil pattern continues to remain a significant image in modern motifs.

Religious trefoils represent the Holy Trinity.
Religious trefoils represent the Holy Trinity.
Jessica Ellis
Jessica Ellis

With a B.A. in theater from UCLA and a graduate degree in screenwriting from the American Film Institute, Jessica is passionate about drama and film. She has many other interests, and enjoys learning and writing about a wide range of topics in her role as a wiseGEEK writer.

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Discussion Comments

@eidetic - I learned about baroque art in an art history survey course I took in college. I remember discussing the trefoil too! Symbolism was an important part of Christian architecture around that time period, so as you said, a lot of churches featured the trefoil.
I took history of baroque art when I was in college, so I'm familiar with the trefoil as a Christian symbol. As the article said, the trefoil shows up a lot in church architecture.

I had to learn to identify certain churches and cathedrals when I was taking my art class, so I learned to tell the difference between differences places by their layout and decoration. I have to admit the trefoils confused me, because so many cathedrals had the same kind of decoration with the same symbols.


@Monika - I've eaten plenty of those trefoil cookies, but I had no clue the trefoil had any symbolism related to the Girl Scouts either. So you're not alone in that!

In fact, I think the only trefoil I associated with any kind of symbolism (until I read this article) was the Irish shamrock. Most Irish themed bars are decorated with a shamrock, and it's a very popular symbol for St. Patrick's Day. So I've always associated the shamrock with Irish heritage.


I was a Girl Scout for years when I was younger, and somehow the symbolism of the trefoil totally escaped my notice. I had no idea the symbol actually stood for anything. I did enjoy the trefoil cookies a lot when cookie-selling season came around though!

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