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: police punishment 
Words: suspension, arrest, classy, custody, fine
classy

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

Category: animal 
Words: fly, fish, wave, bird, waggle

wave