senior vs precedential

senior is a noun but precedential is not a noun.

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

senior (noun)	precedential (noun)
an undergraduate student during the year preceding graduation
a person who is older than you are

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