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: fire, earth, water, blaze, recruit
recruit

Category: aesthetic characteristic 
Words: comfortable, pretty, there, fine, classy
comfortable

Category: type of rigidity 
Words: unyielding, solid, inflexible, firm, amalgamated

amalgamated