"NPS [New Psychoactive Substances] is a category of substances that are fast-evolving, typically volatile and often diversified. The category includes different types of substances in terms of their composition, (il)legitimate use and position in the global drug markets. The great majority of NPS are substances that have no legitimate use, and have no established global large and long-standing markets that compare with the controlled 'traditional' drugs, with few exceptions."
Source
United Nations Office on Drugs and Crime, World Drug Report 2022 (United Nations publication, 2022).