Wear is contact accumulated until it can be seen.
A handle becomes smooth where the hand closes. A floor loses finish along the route between rooms. A stair edge rounds. Paint darkens near a switch. A path appears where enough feet choose the same line.
This evidence can improve design. The worn place identifies reach, traffic, pressure, friction, and the body the object actually serves. A replacement handle can preserve the useful shape. A planned path can move toward the route already being taken.
Wear can also be danger. A polished stair may be slippery. A rounded tool edge may no longer hold. Cracked insulation, corroded pipe, loose masonry, and thinned structure are not patina. The affectionate word should not protect material that has stopped performing safely.
The distinction depends on function and rate. Stable surface change differs from active deterioration. A mark that records use differs from a failure progressing beneath it.
Maintenance often decides which history remains visible. Refinish everything and the record disappears. Preserve everything and the object may become unsafe or unusable. Good repair keeps the evidence that can remain while replacing what can no longer carry its job.
Wear tells the truth about use, but it does not make the repair decision for us.