Lysergic acid diethylamide (LSD), also known colloquially as acid, is a potent psychedelic drug. Effects typically include intensified thoughts, emotions, and sensory perception. At sufficiently high dosages LSD manifests primarily mental, visual, as well as auditory, hallucinations. Effects typically begin within half an hour and can last for up to 20 hours. LSD is also capable of causing mystical experiences and ego dissolution. It is used mainly as a recreational drug or for spiritual reasons. LSD is both the prototypical psychedelic and one of the "classical" psychedelics, being the psychedelics with the greatest scientific and cultural significance.