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: deck, call, galley, bridge, stern
call

Category: window material 
Words: glass, spyhole, handle, coating, knive
knive

Category: body part 
Words: shin, finger, foot, centimeter, elbow

centimeter