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: recruit, replace, sack, heat, fire
heat

Category: police punishment 
Words: prime, fine, jail, suspension, well
well

Category: window material 
Words: glass, plastic, vinyl, fiberglass, fork

fork