Cannabis is an herbal drug that is made from the Cannabis plant. It contains chemicals called cannabinoids. Cannabinoids affect the central nervous system, which includes the brain and nerves. Cannabinoids are found in the highest levels in the leaves and flowers of cannabis. These are the parts of the herb that are used to make medicine. Don't confuse cannabis with hemp. Hemp is a similar plant, but it is grown for the rough parts of the plant (the fiber) as well as for the seeds. Hemp contains very low levels of delta-9-tetrahydrocannabinol (THC), less than 0.3%. Both hemp and cannabis also contain other cannabinoids that are sometimes used as medicine. See specific topics for information on cannabidiol (CBD), cannabidivarin (CBDV), cannabigerol (CBG), and tetrahydrocannabivarin (THCV).Some people take cannabis extract by mouth or as a spray to be applied under the tongue for pain and symptoms of multiple sclerosis.Some people inhale cannabis for nausea, vomiting, an eye disease called glaucoma, and many other conditions, but there is no good scientific evidence to support these uses. Some people also use cannabis to feel good. In this case it is used as a 'recreational drug' and is either taken by mouth or smoked (inhaled). In the U.S., cannabis is illegal under federal law. It is classified as a Schedule I controlled substance. But some states including California, Colorado, Washington, Oregon, Arizona, and others have legalized or decriminalized the use of cannabis. Some countries such as Canada have legalized cannabis use as well.