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: emotional status 
Words: nervous, frustrated, fret, jack, concerned
jack

Category: chocolate food 
Words: cake, fudge, rich, invent, cream
invent

Category: emotional status 
Words: jealous, nervous, content, sad, item

item