appellant vs plaintiff in error

appellant and plaintiff in error both are nouns.

Word	Noun	Adjective	Verb	Adverb
appellant	Yes	Yes	No	No
plaintiff in error	Yes	No	No	No

As nouns, appellant and plaintiff in error are synonyms defined as:

appellant and plaintiff in error: the party who appeals a decision of a lower court

appellant (noun)	plaintiff in error (noun)
the party who appeals a decision of a lower court	the party who appeals a decision of a lower court

appellant (adjective)	plaintiff in error (adjective)
of or relating to or taking account of appeals (usually legal appeals)