Tetrahydrocannabinol

In pharmacology, tetrahydrocannabinol (THC) is "a psychoactive compound extracted from the resin of Cannabis sativa (marihuana, hashish). The isomer delta-9-tetrahydrocannabinol (THC) is  considered the most active form, producing characteristic mood and  perceptual changes associated with this compound. Dronabinol is a  synthetic form of delta-9-THC."