Fret.
Within the context of a guitar, a fret refers back to the raised component on the neck that musicians press the strings in opposition to to alter the pitch of the sounds produced.
In a unique context, “to stress” means to fret or be troubled about one thing. These two meanings of the phrase “fret” are utterly unrelated; that is an instance of a homograph, the place two phrases share the identical spelling however have completely different origins and meanings.