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: animal 
Words: train, fly, jump, leap, grasshopper
train

Category: date status 
Words: current, delayed, postponed, brine, late
brine

Category: physical activity 
Words: hike, duck, sheep, swim, crouch

sheep