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: employment activity 
Words: ban, fire, empower, sack, ground
ground

Category: construction 
Words: windlass, crane, hoist, digger, upraise
hoist

Category: boxing terminology 
Words: box, deck, joker, jab, level

joker