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

Category: body part 
Words: foot, knee, eye, leg, ounce
ounce

Category: bird 
Words: sandpiper, derrick, heron, crane, hoist

derrick