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: baby animals 
Words: fawn, deer, buck, kitten, cajole
cajole

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

Category: boats 
Words: rudder, apron, dock, lifeline, deck

apron