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: kind, down, sad, backward, emotionalities
backward

Category: outdoor sport activity 
Words: dog, swim, hike, hiking, fish
dog

Category: emotional status 
Words: arrest, happy, fine, mad, acceptable

arrest