A friend of mine ranted one day that you should know what you’re doing before you start putting your writing out there for public consumption.
His specific example: someone wrote “died in vein.”
A vein is a stretchy tube inside body which carries de-oxygenated blood back to the heart.
A vane is a metal object which shows wind direction (aka “a weather vane”).
“Vain,” on the other hand, can mean self-absorbed or without purpose or use. When it means “without purpose,” it often comes behind the preposition “in,” as in “all of my studying was in vain; I still failed the test.”
When you can’t remember whether someone died in vain or in vein, just start singing:
“You’re so vain, you probably think this obit is about you.”