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: social gathering 
Words: club, bar, dance hall, discothek, roll
roll

Category: kitchenware 
Words: metal, glass, knifer, dish, cup
metal

Category: employment activity 
Words: replace, sack, fire, blaze, instruct

blaze