In the United States, the word "narcotic" is often misused. While the term "narcotics" is often used to refer to any illicit substance, it technically means a substance derived from opium (opiates) or its synthetic replacements (thegooddrugguide.com).
According to Merriam Webster , A narcotic is a drug (as in opium or morphine) that in moderate doses dulls the senses, relieves pain, and induces profound sleep but in excessive doses causes stupor, coma, or convulsions.
Narcotics are also often confused with stimulants, which in many ways are actually the opposite, as stimulants' effects are alertness and activity.
Examples of narcotics include heroin, morphine and codeine, all of which are highly addictive.
Prescription narcotics (opioids) are prescribed as analgesics, to treat pain.