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: measurement unit 
Words: ounce, foot, kilometer, milimeter, heel
heel

Category: weather 
Words: raining, sunny, fair, ghostly, windy
ghostly

Category: aesthetic characteristic 
Words: endure, even, light, fair, well

endure