Rus vs Kievan Rus'

Rus and Kievan Rus' both are nouns.

Word	Noun	Adjective	Verb	Adverb
Rus	Yes	No	No	No
Kievan Rus'	Yes	No	No	No

As nouns, Rus and Kievan Rus' are synonyms defined as:

Rus and Kievan Rus': the medieval Russian state established by Scandinavian traders in the 9th century; the capital was first in Novgorod and then in Kiev

Rus (noun)	Kievan Rus' (noun)
the medieval Russian state established by Scandinavian traders in the 9th century; the capital was first in Novgorod and then in Kiev	the medieval Russian state established by Scandinavian traders in the 9th century; the capital was first in Novgorod and then in Kiev