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: direction 
Words: kind, descending, down, opposite of up, flat
kind

Category: type of rigidity 
Words: unbending, unyielding, inflexible, firm, streamline
streamline

Category: emotional display 
Words: identity, fawn, woo, flatter, kid

kid