crumb vs cracker crumbs

crumb and cracker crumbs both are nouns.

Word	Noun	Adjective	Verb	Adverb
crumb	Yes	No	Yes	No
cracker crumbs	Yes	No	No	No

As nouns, cracker crumbs is a hyponym of crumb; that is, cracker crumbs is a word with a more specific, narrower meaning than crumb:

crumb: small piece of e.g. bread or cake
cracker crumbs: crumbs of crackers used especially for coating or thickening

Other hyponyms of crumb include breadcrumb.

crumb (noun)	cracker crumbs (noun)
small piece of e.g. bread or cake	crumbs of crackers used especially for coating or thickening
a person who is deemed to be despicable or contemptible
a very small quantity of something