Cannabis smoking (known colloquially as smoking weed or smoking pot) is the inhalation of smoke or vapor released by heating the flowers, leaves, or extracts of cannabis and releasing the main psychoactive chemical, Δ9-tetrahydrocannabinol (THC), which is absorbed into the bloodstream via the lungs. Archaeological evidence indicates cannabis with high levels of THC was being smoked at least 2,500 years ago. As of 2021, cannabis is the most commonly consumed federally illegal drug in the United States, with 36.4 million people (aged 10 years or older) consuming it monthly.
In addition to being smoked and vaporized, cannabis and its active cannabinoids may be ingested, placed under the tongue, or applied to the skin. The bioavailability characteristics and effects of smoking and vaporizing cannabis differ from other cannabis consumption methods in having a more rapid and predictable onset of effect.