Final answer:
THC is the active ingredient in marijuana, differing from opioids like morphine and over the counter pain medications like aspirin, which have different active compounds.
Step-by-step explanation:
THC, or tetrahydrocannabinol, is the active ingredient in marijuana. It is one of many cannabinoids found in the cannabis plant and is known for its psychoactive effects, which can alter mood, perception, and behavior. THC is different from opioids such as morphine and codeine, which are derived from the opium poppy plant, or synthetic opioids like fentanyl. Alcohol is a psychoactive substance as well, but its active ingredient is ethyl alcohol, not THC. Over the counter pain medications like aspirin contain acetylsalicylic acid and others like Tylenol contain acetaminophen, which also do not contain THC.