appendix vs shirttail

appendix and shirttail both are nouns.

Word	Noun	Adjective	Verb	Adverb
appendix	Yes	No	No	No
shirttail	Yes	No	No	No

As nouns, shirttail is a hyponym of appendix; that is, shirttail is a word with a more specific, narrower meaning than appendix:

appendix: supplementary material that is collected and appended at the back of a book
shirttail: a brief addendum at the end of a newspaper article

Other hyponyms of appendix include codicil.

appendix (noun)	shirttail (noun)
a vestigial process that extends from the lower end of the cecum and that resembles a small pouch	fabric forming the tail of a shirt
supplementary material that is collected and appended at the back of a book	a brief addendum at the end of a newspaper article