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: aesthetic characteristic 
Words: variety, fair, alright, pale, flaxen
alright

Category: physical property 
Words: brittleness, protein, bulky, skinny, fat
protein

Category: corporate 
Words: llc, ceo, stiff, common, firm

stiff