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: physical property 
Words: thin, brittleness, heavy, angular momentum, fat
heavy

Category: outdoor sport activity 
Words: kayak, raft, fish, canyoning, dolphin
dolphin

Category: poker 
Words: cards, deck, board, suits, knockout

knockout