noun
1
BAD : This company prefers to employ girls to sale their products.
GOOD : This company prefers to employ girls to sell their products.
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Sale /seIl/ is a noun: 'This new law makes the sale of pirated video tapes a criminal offence.' 'Are you sure the house is for sale?'
The verb is sell /sel/: 'They were selling all the shoes half-price.'
2
BAD : I bought both pairs of shoes on a sale.
GOOD : I bought both pairs of shoes in a sale.
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You buy something in a sale (NOT on ): 'I got the shoes half-price in a sale.'
Compare: 'Shiseido moisturizing cream is on sale in most department stores, priced £4.99.'