This garage sale ad announced, “We can’t take it all with us!”
Perhaps, but if this were really a “stationery bike,” they could have mailed it.
“Stationery,” of course, is a type of writing paper. More broadly, it means office supplies, as when a business calls itself a “stationery store.”
Several years ago when I lived in Philadelphia, a business put up an awning declaring itself The Stationary Store. That store definitely wasn’t going anywhere – it was stationary, or not moving – but what it wanted people to know was that it sold office supplies, that it was The Stationery Store.
Alas, you will find announcements for “stationary” stores around the Internet. You can even buy buttons if you are so inclined. (I’d suggest declining.)
Here’s my advice: To remember the difference, think of stationary meaning staying. With stationery, think pens.
Then again, maybe you really do want to buy a stationery bike. It is possible. I found the one below online, not at the garage sale above. Someone had apparently taken that bike away.