Step 1: Identify the homophone pair.
"Stationary" and "Stationery" sound identical but mean completely different things; confusing them is one of the most common spelling mistakes in English.
Step 2: Use the memory trick to tell them apart.
"StationEry" has an E - think of E for Envelope and pEn (writing materials); "StationAry" has an A - think of A for At a standstill, fixed in place.
Step 3: Apply to the question and confirm.
The word asked about is "Stationary" (with an A), which means not moving, fixed in position; the correct answer is "not moving."
\[ \boxed{\text{Not moving}} \]