Tetrahydrocannabinol (THC) is one of at least 113 cannabinoids identified in cannabis. THC is the principal psychoactive constituent of cannabis. Although the chemical formula for THC (C21H30O2) describes multiple isomers, the term THC usually refers to the Delta-9-THC isomer with chemical name (−)-trans-Δ⁹-tetrahydrocannabinol. Like most pharmacologically active secondary metabolites of plants, THC is a lipid found in cannabis, assumed to be involved in the plant's evolutionary adaptation, putatively against insect predation, ultraviolet light, and environmental stress.
