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.

Q: Category: aesthetic characteristic 
Words: loyal, medium, ghostly, tone, fair

A: loyal
****
Q: Category: elements 
Words: ban, fire, combustion, ground, flame

A: ban
****
Q: Category: activity 
Words: lollygag, waste, fritter, goodbye, sweet roll

A:
sweet roll
****