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.
--------
Question: Category: guitar part 
Words: frustrated, amp, string, fret, headstock

Answer: frustrated


Question: Category: body part 
Words: heel, shin, pound, finger, foot

Answer: pound


Question: Category: kitchenware 
Words: knifer, plate, spyhole, knife, glass

Answer:
spyhole