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.

Category: elements 
Words: pay, cool, combustion, air, fire
pay

Category: outdoor sport activity 
Words: hunt, row, wrestle, fish, hamster
hamster

Category: accomodation 
Words: duplex, studio, flat, paved, squashed

paved