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: physical property 
Words: brittleness, protein, bulky, skinny, fat

Answer: protein


Question: Category: elements 
Words: fire, retire, ice, air, earth

Answer: retire


Question: Category: card games 
Words: pinochle, gin, vodka, hearts, spades

Answer:
vodka