dictator vs emperor

dictator

noun
  • A tyrannical boss or authority figure. 

  • A person who dictates text (e.g. letters to a clerk). 

  • A totalitarian leader of a country, nation, or government. 

  • A magistrate without colleague in republican Ancient Rome, who held full executive authority for a term granted by the senate (legislature), typically to conduct a war. 

emperor

noun
  • The male monarch or ruler of an empire. 

  • A large, relatively valuable marble in children's games. 

  • Any of various butterflies of the subfamily Charaxinae. 

  • Specifically, the ruler of the Holy Roman Empire; the world-monarch. 

  • Any of various large dragonflies of the cosmopolitan genus Anax. 

  • An emperor penguin. 

  • The fourth trump or major arcana card of the tarot deck. 

  • Any monarch ruling an empire, irrespective of gender, with "empress" contrasting to mean the consort of an emperor. 

  • Any fish of the family Lethrinidae. 

How often have the words dictator and emperor occurred in a corpus of books? (source: Google Ngram Viewer )