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.

Category: aesthetic characteristic 
Words: luke, fair, variety, tone, well
luke

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

Category: secretary duty 
Words: motherboard, schedule appointments, schedule, file, type

motherboard