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: social gathering 
Words: club, bar, dance hall, discothek, roll
roll

Category: mode of transportation 
Words: spider, fly, drive, train, soar
spider

Category: boxing terminology 
Words: punch, deck, fight, stern, corner

stern