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: guitar part 
Words: fret, worried, chord, notes, headstock
worried

Category: boats 
Words: bridge, deck, stern, dock, suits
suits

Category: animal 
Words: bats, spider, flutter, fly, ant

flutter