I often see the words stationery and stationary mixed up. It’s an easy mistake to make, and is only an issue in the written word, since both words are pronounced identically and the context is usually clear.

Stationery is a noun, meaning office and desk-type stuff. Think millinery, machinery, that kind of thing.

Stationary is an adjective, meaning motionless. Think customary, arbitrary, and so on.

And of course, because this is English, you get nouns like anniversary and adjectives like blustery :-).

So, remember to keep your stationery stationary and you’ll be fine. Good luck!