A bra, short for brassiere or brassière (US: , UK: or ; French: [bʁasjɛʁ]), is a form-fitting undergarment designed to support or cover a woman's breasts. Bras are designed for a variety of purposes, including general breast support, enhancing breast size, creating cleavage, or for other aesthetic or practical considerations. Swimsuits, camisoles, and backless dresses may have built-in breast support with supportive bra cups. Nursing bras are designed to facilitate breastfeeding. Some people have a medical and surgical need for brassieres, but most wear them for fashion or cultural reasons. There is no evidence that bras prevent breasts from sagging and one study even suggests the opposite (weakening of the breasts' supportive tissue), with the exception of wearing them during sports exercises. Bras have gained importance beyond their mere functionality as a garment. Women's choices about what kind of bra to wear are consciously and unconsciously affected by social perceptions of the ideal female body shape, which changes over time. Bras have become a fashion item and cultural statement that are sometimes purposefully revealed by the wearer or even worn as outerwear, and possess a physiogogic aspect.