Are you clear about the distinction between these two words? Maybe it’s because I’m French but I’m never too sure about which is which!
Stationery (ˈsteɪʃənərɪ) is spelled with an “e”, as in “envelope”, and refers to any kind of writing materials and office supplies.
Stationary (ˈsteɪʃənərɪ) simply mean you are not moving.
Some of us can never remember how many “l” and how many “p” there are in “développer”. I guess it must be even harder to remember for you, foreign speakers of French, since it’s not the same as in English, for instance.
So here’s a little trick I use to make sure I don’t get mixed up :
“Une langue et deux pieds”.
In other words, you’ve got only one tongue (“langue”), but two feet (“pieds”).
Maybe that will help !