I’ve seen this ad a few times, it’s for some toilet bowl cleaner or other. (I’m sure the marketing guys would just flop over dead to hear that I honestly don’t remember what brand.)
Among its other virtues, the ad proclaims that it cleans “invisible stains.”
Every time, I find myself thinking, “If it’s invisible, it’s not a stain. Visibility is part of the definition of a stain.”
Yes, I’m sure it’s cleaning things that are not visible. But those things are not stains.