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: type of sandwich 
Words: meeting, bacon, submarine, toast, club
meeting

Category: guitar part 
Words: truss rod, fret, neck, bored, strap lock
bored

Category: window material 
Words: acrylic, frame, wood, spoon, glass

spoon