sash vs cummerbund

sash and cummerbund both are nouns.

Word	Noun	Adjective	Verb	Adverb
sash	Yes	No	No	No
cummerbund	Yes	No	No	No

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

sash: a band of material around the waist that strengthens a skirt or trousers
cummerbund: a broad pleated sash worn as formal dress with a tuxedo

sash (noun)	cummerbund (noun)
a framework that holds the panes of a window in the window frame	a broad pleated sash worn as formal dress with a tuxedo
a band of material around the waist that strengthens a skirt or trousers