The heart symbol is a picture used to show the idea of the "heart" in a symbolic way. It is a balanced shape made of two curved lines that meet at a point on one side and have a sharp point on the other. This image is not a correct drawing of a real heart. Usually red, the heart symbol represents feelings like love and affection, especially romantic love. Although older versions of this symbol may have existed, the heart shape became common in Europe during the Middle Ages. Sometimes, the heart symbol is shown with an arrow through it, called a "wounded heart," to mean being in love. Other times, it is shown as broken into pieces, called a "broken heart," to mean sadness from lost love.

History

The Indus Valley civilization used peepal leaves in art. A heart-shaped pendant from this civilization was found and is now displayed at the National Museum of India. Between the 5th and 6th centuries BC, the heart shape was used in the Roman world to represent the seeds of a plant called silphium, which may have been used as a contraceptive or an aphrodisiac. Silver coins from Cyrene from the same time show similar designs, sometimes with the silphium plant, and are believed to represent its seed or fruit.

In Japan, the heart symbol has been called Inome, meaning "the eye of a wild boar." It was used to protect against evil spirits and appeared on Shinto shrines, Buddhist temples, castles, and weapons. The oldest examples of this design are found on Japanese sword guards called toran gata tsuba, which were attached to swords from the 6th to 7th centuries. Some of these guards had a hollowed-out heart shape.

The heart shape and its use as a symbol for love began in the late Middle Ages. However, the shape appeared in ancient texts and monuments long before this. Before the 14th century, the heart shape was not linked to the idea of love. Instead, it often represented leaves, such as fig leaves in ancient times or ivy and water-lily leaves in medieval art.

The first known, but debated, use of the heart as a symbol of love appears in a 13th-century manuscript called Roman de la poire. A drawing shows a lover offering a heart-shaped object to a woman. The object resembles a pine cone, as described in medieval anatomy. However, the heart shape is only partially visible, and the object might actually be a pear, as the manuscript is titled Novel of the Pear.

In 1305, the artist Giotto painted an image of charity (called caritas) giving her heart to Jesus Christ. This heart was shaped like a pine cone, as described in anatomy at the time. Giotto’s painting influenced many artists who later depicted charity offering a heart. By the late 14th century, the heart was shown with its point facing downward, a style that became less common by the early 15th century.

The heart shape with a scalloped base, like the modern heart symbol, first appeared in the early 14th century. This design became more common in the 15th century and was used on playing cards by the late 15th century.

Some theories suggest the heart shape in the Middle Ages might have been inspired by ancient symbols, such as the seed of silphium or stylized body parts. However, these ideas are modern and lack clear evidence of a connection between ancient and medieval uses.

Examples of the heart symbol in history include:
– A 13th-century drawing in Roman de la poire showing a lover offering a heart to a woman.
– Giotto’s painting of charity giving a heart to Jesus (1305).
– A depiction of charity on the Florence Baptistery doors (1336).
– A modern-looking heart symbol presented to the goddess Venus in a 15th-century illustration.

Heart shapes have been found on ancient stucco reliefs in Ctesiphon, the Persian capital (90 BC–637 AD).

In 1530, Martin Luther designed a symbol called the Luther rose, which includes a black cross on a heart. Luther explained that the heart reminded him that faith in the Crucified saves people.

Some heart symbols from the 18th century still show the aorta, a blood vessel, at the top of the heart. However, playing cards with the "hearts" suit did not include this detail since the 15th century.

Other examples of the heart symbol include:
– A song called Belle, Bonne, Sage written in the shape of a heart in the Chantilly Codex (late 14th century).
– A 15th-century illustration of the Five Wounds of Jesus, including a wounded heart.
– A 1486 depiction of the Five Wounds.
– A 1500 illustration showing a man placing his heart in a flower named after his lover.
– A 1706 print of the Luther rose.
– A 1540s German deck of playing cards with the hearts suit.
– A 1550s Danish manuscript shaped like a heart, filled with love poems.
– A 1650 painting of Augustine of Hippo holding a heart lit by a ray of divine truth.
– A 1705 painting of the Sacred Heart of Jesus, surrounded by hearts held by angels.
– A 1733 funerary casket holding the heart of a man from Raesfeld.
– An 18th-century illustration of the Sacred Heart of Jesus, based on a vision by Marguerite Marie Alacoque. This heart shows anatomical details, including the aorta and pulmonary artery.
– A 1770 painting of the Sacred Heart by José de…

Heraldry

Heart-shaped symbols in heraldry first appeared in the 12th century. The heart shapes in the coat of arms of Denmark originated from the royal banner of Danish kings, which was based on a seal used as early as the 1190s. These symbols were heart-shaped but did not represent hearts or love. Instead, they likely showed the leaves of the water-lily. Similar heart-shaped designs, also thought to represent water-lily leaves, appeared in other heraldic symbols connected to areas near rivers or coastlines, such as the flags of Frisia.

In heraldry, inverted heart shapes were sometimes used to represent testicles, as seen in the family crest of the Colleoni family from Milan.

A seal linked to William, Lord of Douglas (from 1333), shows a heart shape, which was said to represent the heart of Robert the Bruce. However, the seal's authenticity is uncertain, and it may have been created in the late 14th or 15th century.

Heart-shaped symbols that actually looked like hearts became more common during the early modern period. These were used in religious heraldry, such as the Sacred Heart, and in the coats of arms of wealthy families to symbolize love. Later, hearts also became popular in the coats of arms of cities.

Botanical symbolism

Some questions remain about the connection between the heart symbol and images of the fruit of silphium, a plant that may have gone extinct long ago. Silphium belonged to the Ferula genus and was used as a food and medicine. It was known for its ability to prevent pregnancy and was linked to love and sexuality. Silver coins from ancient Libya, dating to the 6th and 5th centuries BC, show images similar to the heart symbol, sometimes with pictures of the silphium plant. Another plant in the same genus, Ferula assa-foetida, was used as a less effective substitute for silphium. In Tibet and India, this plant is seen as an aphrodisiac, showing another connection between silphium and love.

• Ancient silver coin from Cyrene, Libya showing the heart-shaped "seed" (actually fruit) of silphium
• Example of a heart-shaped fruit in a plant called Heracleum sphondylium, which is related to silphium and belongs to the parsley family, Apiaceae
• Ferula assa-foetida: a large plant in the same genus as silphium, used as a less effective substitute and seen as an aphrodisiac in some regions
• Ferula tingitana: a possible match for the ancient plant known as silphium

Parametrisation

Several methods to describe heart-shaped curves have been developed. The most well-known is the cardioid, a type of curve with one sharp point. However, because the cardioid is missing a point, it may look more like a stylized water-lily leaf, called a seeblatt, than a heart. Other equations, such as the implicit curve (x + y − 1) − x y = 0, can create shapes that more closely resemble a heart.

• Heart curve on TI-89 graphing calculator
• Parametric equation of heart curve on TI-89 graphing calculator