Terminology: opioid vs opiate
“Opioid” is a broad term for drugs that bind opioid receptors and produce opioid effects. “Opiate” is a narrower term for opioid drugs derived directly from opium.
Scope of drug classes
Opioids include both natural and synthetic or semi-synthetic receptor agonists. Opiates include naturally occurring alkaloids derived from opium poppy.
Examples
Opioid examples include morphine, codeine, oxycodone, hydrocodone, fentanyl, methadone, and buprenorphine. Opiate examples include morphine and codeine.
Practical implication
Most clinical references using “opioid” encompass the full range of prescription and illicit receptor-active drugs. Opiate usage typically refers specifically to morphine- and codeine-type natural products.