addict vs junkie

addict and junkie both are nouns.

Word	Noun	Adjective	Verb	Adverb
addict	Yes	No	Yes	No
junkie	Yes	No	No	No

As nouns, junkie is a hyponym of addict; that is, junkie is a word with a more specific, narrower meaning than addict:

Other hyponyms of addict include caffein addict, caffeine addict, drug addict, junky, speed freak.

As nouns, addict and junkie are synonyms defined as:

addict and junkie: someone who is so ardently devoted to something that it resembles an addiction

Other synonyms of addict include freak, junky, nut.

addict (noun)	junkie (noun)
someone who is physiologically dependent on a substance or activity	a narcotics addict
someone who is so ardently devoted to something that it resembles an addiction	someone who is so ardently devoted to something that it resembles an addiction

addict (verb)	junkie (verb)
to cause (someone or oneself) to become dependent (on something, especially a narcotic drug)