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.
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Question: Category: boxing terminology 
Words: deck, ring, head, knockout, glove

Answer: head


Question: Category: measurement unit 
Words: ounce, foot, kilometer, milimeter, heel

Answer: heel


Question: Category: social gathering 
Words: team, roll, club, convention, picnic

Answer:
roll