key
The key is checked before the door closes. Its presence answers a future question: can I get back in? The gesture points toward a boundary that has not yet been crossed.
It depends
where you find it.
A dictionary definition is a beginning. Put two objects into an ordinary situation and the differences between their uses become easier to read.
Before leaving
Two objects carried for different kinds of readiness. A key makes return possible; a comb keeps a small adjustment within reach.
comb
The comb waits for a less definite moment. It may never leave the pocket today. Carrying it preserves an option rather than guaranteeing an action.
Both can be carried without being used. Their difference is in the consequence of absence: one might interrupt a return, the other a private routine. The same pocket can hold unlike kinds of preparedness.
Keep this context in an observation →