The most common definition of democracy is: a government of the people, by the people and for the people.
Basically, in a democracy the decision makers are chosen by the citizens of the country. Every citizen (above 18 or a certain age) has one vote and their vote have the same value. Also, there is a free and fair election. There is also political competition and sufficient choices for people to chose.
For example, in if in some country, decision makers are not chosen by people, then it is not democratic. If in some country, the representatives whom people chose are not real decision makers, then it is not democratic. If in some country, a certain group of people have no vote or their vote has less value than some other group of people, then it is not democratic too. If in some country, the leaders use some unfair practices, like cheating or threatening people, then it is not democratic either. If in some country, there is only one party from which people can chose, then it is also not democratic.
Hope it helps you!!