The term “opiate” is often used to describe any drug or chemical that is either a true opiate, or a synthesized version with similar properties. However, in medical terminology, opiates are the alkaloids that are derived directly from the poppy plant: Morphine, Codeine, and Thebaine. Morphine is the strongest of the alkaloids, followed by codeine, with thebaine being the weakest. From these opiates, opioids are often synthesized.
An opioid is any psychoactive chemical that binds to opioid receptors in the brain. These include opiates as mentioned above, but also include synthetic and semi-synthetic opioids such as oxycodone, hydrocodone, hydromorphone, and fentanyl. Brand names of these products include Vicodin, Percocet, Oxycontin, and Dilaudid. Opioids include all opiates, while opiates are a specific class of opioids.