instruction:
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.
question:
Category: aesthetic characteristic 
Words: medium, just, light, ghostly, fair
answer:
just


question:
Category: secretary duty 
Words: correspondence, schedule, answer calls, keys, file
answer:
keys


question:
Category: boats 
Words: bow, deck, dock, apron, hull
answer:

apron