1) the study of city government, the rights and duties of citizens etc (civics)

2) a state official sent to help and protect her or his fellow citizens in a foreign country (consul)

3) (a country with a) government in which adult citizens freely elect their political representatives to manage public affairs (democracy)

4) (a decision made by) the votes of all qualified citizens (plebiscite)

5) (an amount of) money (to be) paid by citizens to the government (tax)