dictator vs tyrant

dictator and tyrant both are nouns.

Word	Noun	Adjective	Verb	Adverb
dictator	Yes	No	No	No
tyrant	Yes	No	No	No

As nouns, tyrant is a hyponym of dictator; that is, tyrant is a word with a more specific, narrower meaning than dictator:

Other hyponyms of dictator include shogun, strongman, autocrat, despot.

dictator (noun)	tyrant (noun)
a ruler who is unconstrained by law	a cruel and oppressive dictator
a person who behaves in a tyrannical manner	any person who exercises power in a cruel way
a speaker who dictates to a secretary or a recording machine	in ancient Greece, a ruler who had seized power without legal right to it