Mechanistic institutional definitions of a democracy are based on the electoral systems and the powers it hands to officials. There are also soft definitions of democracy that focus on citizens’ rights to form interest groups (pressure groups, political parties, etc.) and judicial protection of citizens.
The quality of a democracy can be rated based on different criteria. Different organisations use different criteria (e.g. Freedom House, Economist Intelligence Unit, Polity IV) which leads to disparate interpretation of which countries have a good democracy. Implications of criteria have been well studies and can be used to make inferences on economic, social and environmental conditions.
Democracies are a reflection of the history of a country in their institutions as much as in their party landscape.
Change in democracies
Erosion of democracy is usually accompanied by restrictions on media and group formation as well as interference with the judicial system (e.g. Hungary). On the other hand strengthening of democracy is usually founded on more free media and an independent judicial system (e.g. Brazil).
Mono-causal explanations for the rise and fall of democracy fail to prove a strong relation. The complexity behind change is still difficult to grasp. Nonetheless, particular development trajectories from autocracy to democracy and vice versa are well understood, but cannot be generalised as no generalisable necessary or sufficient conditions exist.