Lysergic acid diethylamide, LSD, LSD-25, or acid, is a semisynthetic psychedelic drug of the ergoline family. Its unusual psychological effects, which include visuals of colored patterns behind the eyes, a sense of time distorting, crawling geometric patterns, and the loss of the user's sense of identity has made it one of the most widely known psychedelic drugs. It has been used mainly as a recreational drug, an entheogen, and a tool to supplement various practices for transcendence, including in meditation, psychonautics, art projects, and illicit, formerly legal psychedelic therapy.
It is synthesized from lysergic acid derived from ergot, a grain fungus that typically grows on rye, and was first synthesized by Swiss chemist Albert Hofmann. The short form LSD comes from its early code name LSD-25, which is an abbreviation for the German "Lysergsäure-diethylamid" followed by a sequential number.
LSD is sensitive to oxygen, ultraviolet light, and chlorine, especially in solution, though its potency may last for years if it is stored away from light and moisture at low temperature. In pure form it is colorless, odorless, and mildly bitter.