plaintiff in error vs appellant

plaintiff in error and appellant both are nouns.

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

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

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

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

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