A cannabinoid is a class of various chemical compounds that act on cannabinoid receptors, also known as the endocannabinoid system in cells that alter the release of neurotransmitters in the brain. Ligands for these receptor proteins include the endocannabinoids naturally produced by animals in the body; phytocannabinoids found in cannabis and some other plants; and synthetic cannabinoids, artificially manufactured.
The most striking cannabinoid is the phytocannabinoid tetrahydrocannabinol (THC), the primary psychoactive substance in cannabis. Cannabidiol (CBD) is another important component of the plant. There are at least 113 different cannabinoids isolated from cannabis, which show different effects.