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: nutritional value 
Words: iron, heavy, vitamin c, fat, brittleness
brittleness

Category: outdoor sport activity 
Words: hunting, goat, wrestle, fish, raft
goat

Category: temperature 
Words: icy, hot, cool, refreshing, relaxed

relaxed