Each state can adopt elements of more than one system at the same time.
Autocracy. Authoritarianism. Fascism. Castrism. ...
Democracy. Direct democracy. Demagogy, corrupted form of Democracy, according to Aristotle. Indirect democracy (or representative democracy) ...
Oligarchy. Aristocracy. Cleptocracy. Gerontocracy. ...
Theocracy. :
I hope this helps :)