For the record: Things that are on sale are for sale. You sell things that are on sale or that are for sale.
We do not sale things, put things up for sell, or put them on sell. Nay! We sell things, put things up for sale, or put things on sale.
The linguistic epidemic of this sale/sell error may have emerged regionally, but my theory is that eBay was the main carrier of the virus, which has now spread far and wide. Have you browsed eBay or Craigslist ads recently? Then you’ll surely have seen items up “for sell.” Or maybe you’ve encountered ads for items that “must sale.” I saw several items “for sell” that “must sale” on Craigslist today, and I think it’s time someone said something. Now I’ve said it and can move on. As you were.
