pure monopoly, imperfect competition?

I know that monopoly is a form of imperfect competition, but is pure monopoly?
My book firstly says that any market that does not simultaneously have the six conditions of perfect competition is imperfectly competitive, so all markets that are not perfectly competitive are examples of imperfect competition.
Later on in the book it says that imperfect competition ranges from duopoly to markets that approximate to perfect competition, eg. capital market/stock exchange.
I would assume pure duopoly is regarded more extreme than normal monopoly, yet there would still be competition.
The main reason i'm not sure is the face that there is no competition in a pure monopoly so technically it cant be imperfectly competitive?
So I would say that it isn't a form of imperfect competition but i'm not sure, due to the first definition in the textbook.
Should I be considering imperfect substitutes as competition for pure monopoly?

Duopoly = monopoly power between two firms, hence the 'duo' part of the word
Pure monopoly = one firm has total control over the market due to barriers to entry or other prevention of competition.

Sorry if I haven't answered your question, I couldn't really understand most of what you were asking other than the first few lines, I just woke up and my head isn't working right If you're sitting the AQA AS Unit1 exam like me tomorrow, good luck!