If you want to complain about Amazon having power over their suppliers, what you should be calling them is a monopsonist. The difference is pretty simple. A monopoly is a market in which there is only one seller, while a monopsony is a market with only a single buyer.
- Monopoly - in economic theory, a market situation in which there is only one seller.
- Monopsony - in economic theory, a market situation in which there is only one buyer.
I know that some of you are thinking that Amazon is using their monopoly position in the retail market as a club to bully a supplier, in which case you can still say they are using their monopoly power. You could say that, but I think it is better to use the right word.
Plus I just happened to like words, and since the topic of monopolies and monopsonies came up today I thought it would be fun to share the definitions.