seniority vs senior

seniority and senior both are nouns.

Word	Noun	Adjective	Verb	Adverb
seniority	Yes	No	No	No
senior	Yes	Yes	No	No

seniority (noun)	senior (noun)
the property of being long-lived	an undergraduate student during the year preceding graduation
higher rank than that of others especially by reason of longer service	a person who is older than you are

seniority (adjective)	senior (adjective)
	older; higher in rank; longer in length of tenure or service
	used of the fourth and final year in United States high school or college
	advanced in years; (`aged' is pronounced as two syllables)