Complex sentence: Cannabis smoking is the inhalation of smoke or vapors released by heating the flowers, leaves, or extracts of "cannabis" and releasing the main psychoactive chemical, Δ 9-tetrahydrocannabinol (THC), which is absorbed into the bloodstream via the lungs.
Split into simpler sentences: Cannabis smoking is the inhalation of smoke or vapors released by heating the flowers, leaves, or extracts of "marijuana". Smoking releases the main psychoactive chemical in marijuana, Δ 9-tetrahydrocannabinol (THC), which is absorbed into the bloodstream via the lungs.