Inca vs ruler

Inca and ruler both are nouns.

Word	Noun	Adjective	Verb	Adverb
Inca	Yes	No	No	No
ruler	Yes	No	No	No

As nouns, ruler is a hypernym of Inca; that is, ruler is a word with a broader meaning than Inca:

Other hypernyms of Inca include swayer.

Inca (noun)	ruler (noun)
the small group of Quechua living in the Cuzco Valley in Peru who established hegemony over their neighbors in order to create an empire that lasted from about 1100 until the Spanish conquest in the early 1530s	measuring stick consisting of a strip of wood or metal or plastic with a straight edge that is used for drawing straight lines and measuring lengths
a member of the Quechuan people living in the Cuzco valley in Peru	a person who rules or commands
a ruler of the Incas (or a member of his family)