Are sale and sell interchangeable?

No, “sale” and “sell” are not interchangeable.

“Sale” is exclusively used as a noun that denotes the transaction of goods and services for money (e.g., “Those puppies are for sale”).

“Sell” primarily functions as a verb describing the action of trading items or services for monetary payment (e.g., “I want to sell this to the highest bidder”). However, it is sometimes used as a noun to refer to the act of selling, though this usage is less common (e.g., “That’s an easy sell”).