The definition of "monopoly" in terms of government sanction is very common (its one of two common legal definitions); of course, the other common legal definition (and the more common economic definition) is "
the ownership or control of so large a part of the market- supply or output of a given commodity as to stitle competition, restrict the freedom of commerce, and give the monopolist control over prices." [1]
There's obviously a pretty fundamental problem with any discussion of economics which limits itself to the former kind of monopoly and fails to at least discuss the latter kind (even if it uses a different name for it for some reason). And there's equally obviously a problem with any discussion of monopoly in economics which ignores that the use of the term in economics usually means the latter, not the former (while in law, "monopoly" without other qualifications in certain contexts does mean the former, though in other contexts -- e.g., anti-trust, it means the latter.)
There's obviously a pretty fundamental problem with any discussion of economics which limits itself to the former kind of monopoly and fails to at least discuss the latter kind (even if it uses a different name for it for some reason). And there's equally obviously a problem with any discussion of monopoly in economics which ignores that the use of the term in economics usually means the latter, not the former (while in law, "monopoly" without other qualifications in certain contexts does mean the former, though in other contexts -- e.g., anti-trust, it means the latter.)
[1] Both definitions illustrated here: http://thelawdictionary.org/monopoly/