addict

nouns

someone who is so ardently devoted to something that it resembles an addiction
"a golf addict"; "a car nut"; "a bodybuilding freak"; "a news junkie"
someone who is physiologically dependent on a substance; abrupt deprivation of the substance produces withdrawal symptoms
is a type of (narrower)
a person who takes drugs

verbs

to cause (someone or oneself) to become dependent (on something, especially a narcotic drug)
is derived from
is derived from
is derived from