If you want the dictionary definition, just double click on any word.

stationary
vs
stationery

Stationary means not moving.
For example: "The car was stationary."

Stationery is the collective noun for the items needed for writing, such as paper, pens, pencils and envelopes.
For example: "It is the secretary's job to order the stationery?"

!Note - If you have problems with these two words, just remember - 'e' is for envelopes and 'a' is for automobiles.