revenue stamp vs piece of paper

revenue stamp and piece of paper both are nouns.

Word	Noun	Adjective	Verb	Adverb
revenue stamp	Yes	No	No	No
piece of paper	Yes	No	No	No

As nouns, piece of paper is a hypernym of revenue stamp; that is, piece of paper is a word with a broader meaning than revenue stamp:

revenue stamp: a small piece of adhesive paper that is put on an object to show that a government tax has been paid
piece of paper: paper used for writing or printing

Other hypernyms of revenue stamp include sheet, sheet of paper.

revenue stamp (noun)	piece of paper (noun)
a small piece of adhesive paper that is put on an object to show that a government tax has been paid	paper used for writing or printing