Cleavage is the area between a woman's breasts lying over the sternum, and normally refers to what is visible with clothing that includes a low-cut neckline. In some cultures, display of cleavage is considered aesthetic or erotic, and may be associated with garments with low necklines that expose or highlight cleavage, such as ball gowns, evening gowns, lingerie, and swimwear. In these cultures, women have throughout history sought to enhance their physical attractiveness and femininity, within the context of changing fashions and cultural-specific norms of modesty of the time and place. The methods practised in appropriate contexts have included the accentuation and partial display of breasts, including cleavage. In some cultures any display of cleavage may be culturally taboo, illegal or otherwise socially disapproved.
The anatomical term for the area that constitutes a cleavage is intermammary cleft, intermammary sulcus or sulcus intermammarius.
Décolletage is the upper part of a woman's torso, between her waist and neck, comprising her neck, shoulders, back and chest, that is exposed by the neckline of her clothing. However, the term is most commonly applied to a neckline that reveals or emphasizes cleavage.
When the side of the breasts are uncovered, it is known as "side cleavage", "sidewinders" or "sideboob". In early 2010s side cleavage was identified as a fashion trend. Gabriele Hackworthy, fashion director at Harper's Bazaar, said, "The look is unlikely to fade fast, with Yves Saint Laurent and Roberto Cavalli both pushing the silhouette next season."
Many people in Western culture, both male and female, consider breasts an important female secondary sex characteristic and an important aspect of femininity and many women use décolletage that exposes cleavage as part of their physical and sexual attractiveness and to improve their sense of femininity. Display of cleavage with a low neckline is often regarded as a form of feminine flirting or seduction, as much as for its aesthetic or erotic effect. Most men derive erotic pleasure from seeing a woman's cleavage, and some people derive pleasure in their female partner exposing cleavage. When cleavage is enhanced with a push-up bra or exposed by a low neckline it can draw attention. During adolescence, some girls become obsessed with breast shape and cleavage. In South Africa, Wonderbra sponsors a National Cleavage Day during which women are encouraged to display their cleavage. The use of tight clothing and the display of cleavage has been attributed as causes of an increase in breast fetishism, and atypical paraphilia.