user vs addict

user and addict both are nouns.

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

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

Other hyponyms of user include head, tripper.

user (noun)	addict (noun)
a person who makes use of a thing; someone who uses or employs something	someone who is physiologically dependent on a substance or activity
a person who uses something or someone selfishly or unethically	someone who is so ardently devoted to something that it resembles an addiction
a person who takes drugs

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