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 rigidity 
Words: inflexible, tough, taut, firm, leverage
leverage

Category: secretary duty 
Words: organize, support, text, sort mail, file
text

Category: corporate 
Words: combined, firm, common, solid, concerted

solid