2. (foll by with) to associate (oneself) or be associated, esp as a subordinate or subsidiary; bring or come into close connection: he affiliated himself with the Union. b. (as modifier): an affiliate member.
Opiate is a term classically used in pharmacology to mean a drug derived from opium. Opioid, a more modern term, is used to designate all substances, both natural and synthetic, that bind to opioid receptors (including antagonists}. Opiates are alkaloid compounds naturally found in the opium poppy plant Papaver somniferum.
Opium is a drug made from the poppy plant. Poppies grow in many different countries but most poppies today are used to make heroin and opium is much less popular than in was in the past.