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: guitar part 
Words: inlays, concerned, string, notes, fret
concerned

Category: nutritional value 
Words: iron, heavy, vitamin c, fat, brittleness
brittleness

Category: police punishment 
Words: suspension, fine, jail, content, flyaway

content