title role vs name part

title role and name part both are nouns.

Word	Noun	Adjective	Verb	Adverb
title role	Yes	No	No	No
name part	Yes	No	No	No

As nouns, title role and name part are synonyms defined as:

title role and name part: the role of the character after whom the play is named

title role (noun)	name part (noun)
the role of the character after whom the play is named	the role of the character after whom the play is named