dinner napkin vs napkin

dinner napkin and napkin both are nouns.

Word	Noun	Adjective	Verb	Adverb
dinner napkin	Yes	No	No	No
napkin	Yes	No	No	No

As nouns, napkin is a hypernym of dinner napkin; that is, napkin is a word with a broader meaning than dinner napkin:

dinner napkin: a large napkin used when dinner is served
napkin: a small piece of table linen that is used to wipe the mouth and to cover the lap in order to protect clothing

Other hypernyms of dinner napkin include serviette, table napkin.

dinner napkin (noun)	napkin (noun)
a large napkin used when dinner is served	a small piece of table linen that is used to wipe the mouth and to cover the lap in order to protect clothing
	garment consisting of a folded cloth drawn up between the legs and fastened at the waist; worn by infants to catch excrement