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.

[Q]: Category: temperature 
Words: cold, hot, cool, popular, relaxing
[A]: popular


[Q]: Category: social gathering 
Words: convention, club, discothek, hamburger, dance hall
[A]: hamburger


[Q]: Category: bird 
Words: mallet, duck, winch, crane, ostrich
[A]:
winch