The heart symbol is a picture used to show the idea of a heart in a symbolic way. It is a balanced shape made of two similar curves that meet at one end and have a point at the other. This symbol is not a correct drawing of a real heart. Usually red, it represents feelings like love and affection, especially romantic love. Although older versions might exist, this heart shape became common in Europe during the Middle Ages. Sometimes, it is shown with an arrow through it, called a "wounded heart," which means being in love. Another version is a "broken" heart, split into pieces, which shows sadness from a lost love.

History

Peepal leaves were used in artwork by the Indus Valley civilization. A heart-shaped pendant from this civilization has been found and is now displayed in the National Museum of India. In the 5th–6th century BC, the heart shape was used in the Roman world to represent the seeds of the silphium plant, which may have been used to prevent pregnancy or increase sexual desire. Silver coins from Cyrene from this time show a similar design, sometimes with a 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," and was used to protect against evil spirits. These symbols 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 between the 6th and 7th centuries. Some of these guards had a hollowed-out heart shape.

The heart shape and its use to represent love began in the late Middle Ages. However, the shape itself appeared in many ancient writings and carvings. Before the 14th century, the heart shape was not connected to the idea of love. Instead, it often showed leaves, like fig leaves from ancient times or ivy and water-lily leaves in medieval art.

The first known, but debated, use of a heart as a symbol of love dates to the 1250s. It appears in a picture from a French manuscript called Roman de la poire. In the image, a kneeling lover offers his heart to a lady. The heart in the picture looks like a pine cone, as described in medieval anatomy. However, the heart shape is only partly visible, and the object might actually be a pear, as the manuscript is titled Novel of the Pear. This connection remains unclear.

In 1305, the artist Giotto painted an image in the Scrovegni Chapel showing an allegory of charity (caritas) giving her heart to Jesus. This heart was shaped like a pine cone, as described in medieval anatomy. Giotto’s painting influenced later artists, who also showed charity giving a heart. Over time, the heart’s point began to face upward instead of downward.

The modern heart shape, with a dent at the bottom, first appeared in the early 14th century. It 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 seeds of the silphium plant or stylized body parts. However, these ideas are not proven, as there is no clear link between ancient symbols and the heart shape used later.

Examples of the heart symbol include:
– A 13th-century manuscript showing a lover giving his heart to a lady (Roman de la poire).
– Giotto’s 1305 painting of charity giving a heart to Jesus.
– A 1336 depiction of charity on the Florence Baptistery doors.
– A 1407 illustration showing a heart symbol presented to Venus.

Heart shapes have been found on ancient wall carvings in Ctesiphon, a Persian city from around 90 BC to 637 AD.

In 1530, Martin Luther designed a symbol called the Luther rose. It includes a black cross on a heart, representing faith in Jesus. Luther explained that the heart reminded him of the importance of faith.

In some religious art, the aorta (a blood vessel) was shown at the top of the heart symbol, especially in depictions of the Sacred Heart. This detail was common in the 18th century but not in playing cards since the 15th century.

Other examples include:
– A 14th-century song titled Belle, Bonne, Sage written in the shape of a heart.
– A 15th-century manuscript showing the wounded heart of Jesus.
– A 1486 illustration of the Five Wounds.
– A 1500 miniature showing a man placing his heart in a flower.
– A 1706 print of the Luther rose.
– A 1540s German deck of playing cards with a hearts suit.
– A 1550s Danish manuscript shaped like a heart.
– A 1650 painting of Augustine of Hippo holding a glowing heart.
– A 1705 painting of the Sacred Heart with hearts held by angels.
– A 1733 funerary casket with a lead heart.
– An 18th-century image of the Sacred Heart from a vision, showing anatomical details.
– A 1770 painting of the Sacred Heart by José de.

Heraldry

Heart-shaped symbols in heraldry first appeared in the 12th century. The hearts on the coat of arms of Denmark are linked to the royal banner of Danish kings, which was based on a seal from the 1190s. These symbols were heart-shaped, but they did not originally represent hearts or love. Instead, they are believed to have shown the leaves of the water-lily. Similar heart-shaped symbols that represented water-lily leaves appear in heraldic designs from areas near rivers or coastlines, such as the flags of Frisia.

In heraldry, inverted heart symbols 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 is 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 in later periods. These were used in religious heraldry, such as the Sacred Heart, and in the coats of arms of non-royal families to symbolize love. Later, hearts also became popular elements in the coats of arms of cities.

Botanical symbolism

There have been questions about the connection between the traditional heart symbol and pictures of the fruit of silphium, a plant that may have gone extinct long ago. Silphium belonged to the genus Ferula and was used as a seasoning and medicine in ancient times. It had properties that could act as a contraceptive and induce abortions, which linked it to love and sexuality. Silver coins from ancient Libya, dating to the 6th to 5th centuries BC, show images similar to the heart symbol, sometimes with pictures of the silphium plant. A related plant, Ferula assafoetida, was used as a less effective substitute for silphium. In Tibet and India, assafoetida is considered an aphrodisiac, showing another connection between silphium and love.

• Ancient silver coin from Cyrene, Libya showing the heart-shaped "seed" (actually the fruit) of silphium
• Example of a heart-shaped mericarp fruit in a plant (Heracleum sphondylium), which, like silphium, belongs to the parsley family, Apiaceae
• Ferula assa-foetida: a type of giant fennel in the same genus as silphium, with similar properties but less effective as a substitute
• Ferula tingitana: a possible match for the ancient plant known as silphium

Parametrisation

Several ways to describe curves that look like hearts have been studied. The most famous is the cardioid, a special type of curve with one pointy tip. However, because the cardioid does not have a pointed end, it can also be compared to a stylized water-lily leaf, called a seeblatt, instead of 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