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: aesthetic characteristic 
Words: cool, trustworthy, milky, fair, well
trustworthy

Category: ocean 
Words: flow, current, course, moon, dastards
dastards

Category: activity 
Words: doughnut, blow, goodbye, dally, fritter

doughnut