Marijuana (grass, pot, weed) is the common name for a crude drug made from the plant Cannabis sativa. The main mind-altering (psychoactive) ingredient in marijuana is THC (delta-9-tetrahydrocannabinol), but more than 400 other chemicals also are in the plant. A marijuana "joint" (cigarette) is made from the dried particles of the plant. The amount of THC in the marijuana determines how strong its effects will be. The type of plant, the weather, the soil, the time of harvest, and other factors determine the strength of marijuana. The strength of today's marijuana is as much as ten times greater than the marijuana used in the early 1970s. This more potent marijuana increases physical and mental effects for the user. Hashish, or hash, is made by taking the resin from the leaves and flowers of the marijuana plant and pressing it into cakes or slabs. Hash is usually stronger than crude marijuana and may contain five to ten times as much THC. Pure THC is almost never available, except for research. Substances sold as THC on the street often turn out to be something else, such as PCP.