There could be many forms of democracy. One is a multi-party system with elections every four or five years. Another could be a single-party system. All you need is some kind of democratic process, i.e. so people can have a say and can in different ways participate in national, social, political affairs etc.

It's not hard to imagine a single-party system being more democratic than a multi-party system. There's more to ensuring democracy than just having two or more political parties to choose from on a piece of paper.