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: elements 
Words: fire, retire, ice, air, earth
Example Output: retire

Example Input: Category: corporate 
Words: solid, sustainability, streamline, firm, private
Example Output: solid

Example Input: Category: ocean 
Words: signal, timely, brine, flow, current
Example Output:
timely