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: bird 
Words: neck, tackle, derrick, crane, steam roller
steam roller

Category: emotional status 
Words: ecstatic, excited, content, activity, angry
activity

Category: emotional status 
Words: relaxed, mad, fine, alright, probation

probation