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: measurement unit 
Words: meter, inch, foot, heel, pound
heel

Category: boats 
Words: head, hull, knockout, deck, dock
knockout

Category: emotional status 
Words: kind, down, miserable, emotional, up

up