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: obese, heavy, area, chunky, fat

Answer: heavy


Question: Category: animal 
Words: trap, dog, fish, tiger, horse

Answer: trap


Question: Category: aesthetic characteristic 
Words: cool, fair, ghostly, deal, size

Answer:
deal