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: type of rigidity 
Words: rigged, firm, unyielding, streamline, taut

Answer: streamline


Question: Category: aesthetic characteristic 
Words: well, milky, variety, tone, fair

Answer: well


Question: Category: chocolate food 
Words: rich, fudge, cupcake, smear, cookies

Answer:
smear