Lycra is a man-made fiber that includes synthetic polymers. Although the exact content of Lycra is a trade secret, according to the Royal Society of Chemistry, the United Kingdom's professional association of chemists, the manufacturer calls Lycra an elastane fiber.
Many types of clothing contain Lycra, but the fiber usually makes up only a portion of the fabric content of a garment, depending on the amount of elasticity that is needed. Swimwear often contains as much as 60 percent Lycra to make the bathing suits close fitting and stretchable. According to Invista, a Lycra fiber stretches up to seven times its original length.