Dictionary Time?

Who is it that defines what an addiction is?
Webster Say's this; "compulsive need for and use of a habit-forming substance (as heroin, nicotine, or alcohol) characterized by tolerance and by well-defined physiological symptoms upon withdrawal; broadly : persistent compulsive use of a substance known by the user to be harmful"
Some people know that they have addictions others may not, and some may have habits that they think are o.k. but in all reality their habits are just as much of an addiction as an admitted addict.
What if you don't have withdraw symptoms that are easily seen? like what you might get with heroin, alcohol or nicotine?
And who is it that decides what the tolerance level is? Society? The Church? your family?
Just looking for opinions.