I used to be oblivious to this, but now I know, misuse increasingly sticks out like a sore thumb:
- “Less” is for an amount of bulk stuff you’re not counting in discrete units – less water, less food, less stock
- “Fewer” is for discrete, countable things – fewer drinks, fewer meals, fewer items at a checkout
So if the sign at your checkout says “10 items or less”, it’s just wrong. Silly sign.