Final answer:
An opioid is a substance or mechanism that has pain-relieving properties. Opioids have analgesic properties and can decrease pain. The body produces endogenous opioids that bind to opioid receptors and reduce pain.
Step-by-step explanation:
An opioid is a substance or mechanism that has pain-relieving properties. Opioids are a category of drugs that includes heroin, morphine, methadone, and codeine. They have analgesic properties, meaning they decrease pain. The body also produces endogenous opioids, which are naturally occurring compounds that bind to opioid receptors and reduce pain.