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: physical property 
Words: brittleness, large, fat, area, calcium
calcium

Category: type of rigidity 
Words: rigged, firm, unyielding, streamline, taut
streamline

Category: geographical property 
Words: lined, mountain, flat, cabin, elevation

cabin