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: inflexible, tough, taut, firm, leverage

Answer: leverage


Question: Category: physical property 
Words: large, fat, capacitance, calories, ugly

Answer: calories


Question: Category: accomodation 
Words: house, flat, mansion, apartment, plane

Answer:
plane