I was in a meeting with a dozen people, when someone said, "We are facing a windfall because we have eight people leaving in the next two months." And later,"Since these people are leaving, we are bracing for a windfall."
Well, of course, that's the opposite meaning of "windfall." It actually means an unexpected or undeserved gain, not a dramatic loss.
Should I have spoken up and corrected this mistake? Some say yes. Those who know correct English usage, some say (and here I'm thinking of John Simon, who recommended this in his book Paradigms Lost), should defend it and correct it; we should work to preserve and uphold high standards of English usage in speaking and writing. But it makes you look like a snob.
I usually let it go unless it's my own kids.
On that point, my daughter, 16, has taken to saying "whenever" in place of "when." She says, "Whenever Steve was at our house last week, he helped me fix the fence."
I tried to explain that by using "whenever" she is saying "each time he was at the house" and that if she means a particular time, she should say "When Steve was at our house . . ."
Of course she eagerly noted this in her "Correct English Usage" notebook, which she carries with her always, and then thanked me for the valuable insight.