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: animal 
Words: bird, fish, fly, drive, eagle
drive

Category: aesthetic characteristic 
Words: ghostly, milky, windy, fair, texture
windy

Category: animals 
Words: geese, crouch, duck, elephant, mallet

crouch