sale vs rummage sale

sale and rummage sale both are nouns.

Word	Noun	Adjective	Verb	Adverb
sale	Yes	No	No	No
rummage sale	Yes	No	No	No

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

sale (noun)	rummage sale (noun)
a particular instance of selling	a sale of donated articles
an occasion (usually brief) for buying at specially reduced prices
the general activity of selling
an agreement (or contract) in which property is transferred from the seller (vendor) to the buyer (vendee) for a fixed price in money (paid or agreed to be paid by the buyer)
the state of being purchasable; offered or exhibited for selling