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: 70, variety, color, fair, light
70

Category: boats 
Words: hull, deck, rudder, check, lifeline
check

Category: elements 
Words: fire, cool, water, ban, ice

ban