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: ban, fire, combustion, ground, flame
Example Output: ban

Example Input: Category: guitar part 
Words: truss rod, fret, neck, bored, strap lock
Example Output: bored

Example Input: Category: emotional status 
Words: happy, fine, mad, level, decent
Example Output:
level