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: boxing terminology 
Words: corner, fold, deck, knockout, level
fold

Category: aesthetic characteristic 
Words: well, milky, variety, tone, fair
well

Category: animal 
Words: fly, beetle, run, eagle, walk

walk