Methods of consumption

Cannabis is prepared for human consumption in several forms:
Marijuana or ganja: the flowering tops of female plants, from less than 1% THC to 22% THC; the wide range is probably one of the reasons for the conflicting results from different studies.
Hashish or charas: a concentrated resin composed of heated glandular trichomes that have been physically extracted, usually by rubbing, sifting, or with ice.
Kief: (1) the chopped flowering tops of female cannabis plants, often mixed with tobacco; (2) Moroccan hashish produced in the Rif mountains; (3) sifted cannabis trichomes consisting of only the glandular "heads" (often incorrectly referred to as "crystals" or "pollen"); (4) the crystal (trichomes) left at the bottom of a grinder after grinding marijuana, then smoked.
Bhang: a beverage prepared by grinding cannabis leaves in milk and boiling with spices and other ingredients.

Hashish
These forms are not exclusive, and mixtures of two or more different forms of cannabis are frequently consumed. Between the many different strains of cannabis and the various ways that it is prepared, there are innumerable variations similar to the wide variety of mixed alcoholic beverages that are consumed.

Smoking

Joints

Vaporization
A vaporizer heats herbal cannabis to 365–410 °F (185–210 °C), which turns the active ingredients into gas without burning the plant material (the boiling point of THC is 200°C at 0.02 mm Hg pressure, and somewhat higher at standard atmospheric pressure). Toxic chemicals are released at much lower levels than by smoking, although this may vary depending on the design of the vaporizer and the temperature at which it is set. A MAPS-NORML study using a Volcano™ vaporizer reported 95% THC and no toxins delivered in the vapor. However, an older study using less sophisticated vaporizers found more toxins. The effects from a vaporizer are noticeably different to that of smoking cannabis. Users have reported a more euphoric hallucinogen type high, because the vapor contains more pure THC.

Eating
As an alternative to smoking, cannabis may be consumed orally. Although hashish is sometimes eaten raw or mixed with water, THC and other cannabinoids are more efficiently absorbed into the bloodstream when dissolved in ethanol, or combined with butter or other lipids. The time to onset of effects is usually about an hour and may continue for a considerable length of time, whereas the effects of smoking herbal cannabis are almost immediate.
Smoking cannabis results in a significant loss of THC and other cannabinoids in the exhaled smoke, by decomposition on burning, and in smoke that is not inhaled. In contrast, all of the active constituents enter the body when cannabis is ingested. It has been shown that the primary active component of cannabis, Δ9-THC, is converted to the more psychoactive 11-hydroxy-THC by the liver. Titration to the desired effect by ingestion is much more difficult than through inhalation.

Other methods
Cannabis material can be leached in high-proof spirits (often grain alcohol) to create “Green Dragon”. This process is often employed to make use of low-potency stems and leaves.
Cannabis can also be consumed as a tea. Although THC is lipophilic and only slightly water soluble (with a solubility of 2.8 grams per liter), enough THC can be dissolved to make a mildly psychoactive tea. However, water-based infusions are generally considered to be an inefficient use of the herb.
In 2006, hollowed-out gumballs filled with cannabis material and labeled as “Greenades” were distributed by high school students in the U.S.