https://www.merriam-webster.com/dictionary/addiction

Dsm5: Taking the substance in larger amounts or for longer than you're meant to

Wanting to cut down or stop using the substance but not managing to

Spending a lot of time getting, using, or recovering from use of the substance

Cravings and urges to use the substance

Not managing to do what you should at work, home, or school because of substance use

Continuing to use, even when it causes problems in relationships

Giving up important social, occupational, or recreational activities because of substance use

Using substances again and again, even when it puts you in danger

Continuing to use, even when you know you have a physical or psychological problem that could have been caused or made worse by the substance

Needing more of the substance to get the effect you want (tolerance)

Development of withdrawal symptoms, which can be relieved by taking more of the substance

Note that the dsm5 categorizations only needs a couple of those for it to count as a mild substance use disorder. A daily habit you can't stop, cravings/urges, and a history of familial problems made worse by it, and withdrawal symptoms are more than enough to count without regard to the amount. I'm addicted to caffeine as are most adults I know. Hell some people can fit this definition with junk food and that counts and is valid.