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: flutter, fly, bats, eagle, pounce
flutter

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

Category: emotional status 
Words: amp, angry, concerned, sad, fret

amp