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.

Example Input: Category: type of rigidity 
Words: rigged, firm, unyielding, streamline, taut
Example Output: streamline

Example Input: Category: boats 
Words: lifeline, stern, fold, deck, rudder
Example Output: fold

Example Input: Category: chocolate food 
Words: brownies, fudge, cake, replace, pudding
Example Output:
replace