Given a category and a set of five words, find the word from the set that does not belong (i.e. is the least relevant) with the other words in the category. Words are separated by commas.

Category: body part 
Words: elbow, foot, knee, inch, hand
inch

Category: guitar part 
Words: fret, worried, chord, notes, headstock
worried

Category: secretary duty 
Words: file, keys, organize, errands, correspondence

keys