Stationary or stationery? They're just one letter off, but that pesky little "e" or "a" changes the meaning of these words entirely. Stationery is writing paper or writing materials such as pens, envelopes, and ink. The word is derived from the Middle Latin stationarius, "stationary seller." In the Middle Ages roving peddlers often sold writing supplies, moving their wares from "station" to "station." Switch that final "e" for an "a" and to be stationary is to be unmoving.