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: secretary duty 
Words: errands, schedule appointments, image, make coffee, file
Example Output: image

Example Input: Category: physical property 
Words: obese, fat, vitamin c, heavy, thin
Example Output: vitamin c

Example Input: Category: elements 
Words: fire, ground, scold, burn, combustion
Example Output:
scold