gateway drug: a habit-forming drug that is not addictive but its use may lead to the use of other addictive drugs
entity: that which is perceived or known or inferred to have its own distinct existence (living or nonliving)
tellurium: a brittle silver-white metalloid element that is related to selenium and sulfur; it is used in alloys and as a semiconductor; occurs mainly as tellurides in ores of copper and nickel and silver and gold