Cannabis is a genus of flowering plants that includes Cannabis sativa, Cannabis indica, and Cannabis ruderalis. Indigenous to Central and South Asia, cannabis has long been used for fiber, seeds and oils, and for medicinal and recreational purposes. Cannabis is commonly referred to as marijuana, among other names, when as a psychoactive drug or as medicine. Tetrahydrocannabinol (THC) is the principal psychoactive constituent (cannabinoid) and is only found in the female cannabis plant.
The plant name cannabis is from Greek (kánnabis), via Latin, originally a Scythian or Thracian word, also loaned into Persian as kanab. English hemp (Old English hænep) may be an early loan (predating Grimm's Law) from the same Scythian source.
- Smoking - Cannabis may be inhaled by burning its leaves, flowers and extracts in a variety of forms.
- Vaporizer - An alternative to smoking, vaporizing allows inhalation while avoiding certain by-products.
- Edibles - Cannabis may be consumed in a variety of edible forms such as cookies
- Concentrates - such as oil
- Tea - cannabis tea is an infusion of cannabis in hot water.
Cannabis is a popular recreational drug around the world, only behind alcohol, caffeine and tobacco. In the United States alone, it is believed that over 100 million Americans have tried Cannabis, with 25 million Americans having used it within the past year.
Medical cannabis or medical marijuana refers to the use of cannabis and its constituent cannabinoids, such as tetrahydrocannabinol (THC), as medical therapy to treat disease or alleviate symptoms. The Cannabis plant has a history of medicinal use dating back thousands of years across many cultures. 
- Histories (September 20, 2010), Herodotus
- Introduction (February 11, 2011), National Organization for the Reform of Marijuana Laws
- Journal of Ethnopharmacology (2006), doctordeluca.com