addict

v. cause to become dependent on, cause to become addicted to (a habit-forming substance); compulsively devote oneself to someone or something

n. one who is devoted to a certain habit; habitual drug user

An addiction is a recurring compulsion by an individual to engage in some specific activity, despite harmful consequences to the individuals health, mental state or social life. The term is often reserved for drug addictions but it is sometimes applied to other compulsions, such as problem gambling, compulsive overeating, and hyperreligiosity Factors that have been suggested as causes of addiction include genetic, biological/pharmacological and social factors.
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Ad·dict n. One who is addicted, as to narcotics or a compulsive activity. addict, n an individual who has developed physiologic or psychologic [more]Addict - Community and Resources

Noun
1. someone who is so ardently devoted to something that it resembles an addiction; "a golf addict"; "a car nut"; "a news junkie"
(synonym) nut, freak, junkie, junky
(hypernym) enthusiast, partisan, partizan
(hyponym) gym rat
(derivation) hook
2. someone who is physiologically dependent on a substance; abrupt deprivation of the substance produces withdrawal symptoms
(hypernym) drug user, substance abuser, user
(hyponym) caffeine addict, caffein addict
(derivation) hook
Verb
1. to cause (someone or oneself) to become dependent (on something, especially a narcotic drug)
(synonym) hook
(hypernym) habituate, accustom
(entail) use, habituate
(derivation) addiction

n. addict, one who is devoted to a certain habit; habitual drug user