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.

[EX Q]: Category: bird 
Words: concrete pourer, flamingo, egret, crane, duck
[EX A]: concrete pourer

[EX Q]: Category: elements 
Words: let go, flame, inferno, fire, water
[EX A]: let go

[EX Q]: Category: animals 
Words: lion, cow, duck, cat, stoop
[EX A]:
stoop