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: personal characteristic 
Words: freezing, calm, positive, cool, popular
freezing

Category: corporate 
Words: unyielding, firm, streamline, llc, private
unyielding

Category: mode of transportation 
Words: wave, ant, train, flutter, fly

ant