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: weather 
Words: even, tangle, mild, fair, 70
even

Category: window material 
Words: glass, coating, panel, spatula, lead
spatula

Category: employment activity 
Words: combustion, hire, fire, let go, recruit

combustion