sale has 3 distinct synonyms spread across 2 of its 5 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a particular instance of selling
“he has just made his first sale”
an occasion (usually brief) for buying at specially reduced prices
“they held a sale to reduce their inventory”
the state of being purchasable; offered or exhibited for selling
“you'll find vitamin C for sale at most pharmacies”
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 salesman faxed the sales agreement to his home office”
Synonyms, antonyms and the broader and narrower relations for sale come from Princeton University’s WordNet. Full sources and licences.