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: police punishment 
Words: fine, prime, firstrate, comfortable, ticket
comfortable

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

Category: emotional status 
Words: sad, remorseful, down, ashamed, sliding

sliding