^ Can't speak of crack as I have no experience with that, but I do know plenty of casual meth users.
The definitions of using/abusing and addiction, which may include physical and/or psychological dependence are all subjective and overlap. Abusing to one may be using to another. Addiction to one may simply be dependance to another.
This whole "everything/x is subjective" argument only goes so far. Words are assigned meanings, just like objects are assigned words, with the intent of creating an mutual language understandable by all. Definitions are based on objective truths, and they're recognised as the same by people through intelligibility; for example, we know that "abuse" is, by definition, something which is exploited generally for monetary or emotional gain.
The
meaning of a word, however, is relatively subjective as it changes depending on the culture in which it's used; for example, in the court of law or at a crime scene the word "abuse" can be associated with "domestic abuse", something which isn't specifically detailed in the definition of the word "abuse".
My point is that, while things are subjective, a belief, however subjective, can be justified through reason (or other methods such as emotions) and the
level of objectivity is what makes a certain belief more valid than other less deserving beliefs. The point of this thread is not only to establish what sort of category we, as individuals, fit under appropriately, but to reach a valid conclusion on what the difference between the three words are in terms of drug-use. Talking about whether the discussion is worth it or not is just discussing semantics, and it's as redundant as the inherent discussion brought up in this thread.
I haven't exactly thought about the topic, but I suppose I could chime in;
Drug-use could be "use" in general, or, more specifically, it (the meaning) could be use of drugs with little to no negative effects as a consequence, including post-cravings and excessive use.
Drug-abuse could just mean Using a drug excessively or with no regard of the drug's potential consequences, nor with any moderation.
Drug-addiction could mean A constant desire for a certain drug as a result of psychological/physiological withdrawal. This includes any desire for non-reality as well, and using drugs as a means to constantly achieve that desire.
A drug addict can use in moderation, but only to keep certain withdrawals at bay. A drug user respects the boundaries in which drug-use becomes dangerous and/or a negative impact in general.
That's my definition of it, anyway. I don't consider myself a drug abuser, in retrospect, but just an addict and a user in general
Sorry its hard to tell emotional intent behind text but I wasn't offended or angry 
