Unfortunately this question is very complicated and doesn't have an easy answer! Political scientists don't think of countries as "Democracy: Yes/No." Instead, countries are giving a score on most to least democratic.
A few characteristics that we look for to see if countries are more democratic are: 1) free and fair elections held at regular intervals (not necessarily every x years), 2) ability to get information from a source other than the govt (free press, and related), 3) inclusion of all adult citizens, 4) protection of civil liberties & rights, 5) separation of powers
The Polity score is the most often used rating of how democratic a country is. You can check it out on their website, or just by Googling "Polity scores" to check out the scores for each country, rated from total autocracy (not at all democracy) to full democracy.
Hope that helps!