selling vs sale

selling and sale both are nouns.

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

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

selling (noun)	sale (noun)
the exchange of goods for an agreed sum of money	a particular instance of selling
	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