The heart symbol or "heart shape" (♥) is an ideograph used to express the idea of the "heart" in its metaphorical or symbolic sense as the center of emotion, including affection and love, especially (but not exclusively) romantic love.
The combination of the "heart shape" and its use within the "heart" metaphor developed at the end of the Middle Ages. With possible early examples or direct predecessors in the 13th to 14th century, the familiar symbol of the heart representing love developed in the 15th century, and became widely popular in the 16th. Before the 14th century, the "heart shape" was not associated with the meaning of the "heart" metaphor. The geometric shape itself is found in much earlier sources, but in such instances does not depict a "heart", but typically foliage, in examples from antiquity fig leaves, and in medieval iconography and heraldry typically the leaves of ivy and of the water-lily.
The first known depiction of a heart as a symbol of romantic love dates to the 1250s. It occurs in a miniature decorating a capital S in a manuscript of the French Roman de la poire (National Library FR MS. 2086, plate 12). In the miniature, a kneeling lover (or more precisely, an allegory of the lover's "sweet gaze" or douz regart) offers his heart to a damsel. The heart here resembles a pine-cone (held "upside-down", the point facing upward), in accord with medieval anatomical descriptions. Giotto in his 1305 painting in the Scrovegni Chapel (Padua) shows an allegory of charity handing her heart to Christ, and this heart is depicted in the pine-cone shape based on anatomical descriptions (still held "upside-down"). Giotto's painting exerted considerable influence on later painters, and the motive of Caritas offering a heart is shown by Taddeo Gaddi in Santa Croce, by Andrea Pisano on the bronze door of the south porch of the Baptisterium in Florence (c. 1337), by Ambrogio Lorenzetti in the Palazzo Publico in Sienna (c. 1340) and by Andrea da Firenze in Santa Maria Novella in Florence (c. 1365). The convention of showing the heart point-upward switches in the late 14th century and becomes rare in the first half of the 15th century.
The "scalloped" shape of the now-familiar heart symbol, with a dent in its base, first arises in the early 14th century, at first only lightly dented, as in the miniatures in Francesco Barberino's Documenti d'amore (before 1320); a slightly later example with a more pronounced dent is found in a manuscript from the Cistercian monastery in Brussels (MS 4459–70, fol 192v. Royal Library of Belgium). The convention of showing a dent at the base of the heart thus spread at about the same time as the convention of showing the heart with its point downward. The modern indented red heart has been used on playing cards since the late 15th century.
Various hypotheses attempted to connect the "heart shape" as it evolved in the late medieval period with instances of the geometric shape in antiquity. Such theories are modern, proposed from the 1960s onward, and they remain speculative, as no continuity between the supposed ancient predecessors and the late medieval tradition can be shown. Specific suggestions include: the shape of the seed of the silphium plant, used in ancient times as an herbal contraceptive, and stylized depictions of features of the human female body, such as the female's buttocks, pubic mound, or spread vulva. a heart is not the only symbol for love.