καθαρίζονται [12 verses](verb 3rd pl pres ind mp) "Be clean" is katharizo, which means "to clean," "to clear the ground of weeds," "prune away," "to remove dirt," "to purify,"and "to remove impurities." It is also used to describe the removal of the inedible parts from grain (winnowing), clearing weeds from a field, pruning a plant and so on.-- The Greek word translated as "be clean," means to remove dirt. It is used for a lot of specific types of "cleaning" including cleansing a person of leprosy but it also has a general meaning of "purifying" anything.

καθαρόν. [5 verses](adj sg masc acc) "Clean" is katharos, which means "physically clean," "spotless," "clear," "pure (water)," "clear of objects," "free of contamination," "clear of debt," "genuine," "pure of birth," "without blemish," and "sound." -- The Greek word translated as "clean" means "physically clean," "spotless," "free of contamination," "clear of debt," "genuine," "pure of birth," "without blemish," and "sound."

καθέδρας [4 verses](noun pl fem acc)  "Seat" is kathedra, which means "a chair," "a seat" "a sitting position," "the sitting part," "the posterior," "sitting idle," "inaction," "the chair [of a teacher]," "a session," and "a throne," is used to denote a position of power. From the Greek kata("down") hedraios ("to settle") .

καθηγηταί, [1 verse](noun pl masc dat) "Masters" is kathêgêtês, which means "guide" and "teacher" and "professor."  - "Master" here is the same root as "masters" above.

καθημένοις [13 verses](part pl perf mid masc dat) "Sitting" is kathemai, which means "to sit," "to be seated," "to sit still," "to sit quiet," "to reside," and "to be placed."  - "Sitting" is a Greek verb that means to "be seated," "sit," especially of courts, councils, assemblies, etc.  The sense of being put in a position of authority as we would say "chair." It also means to "sit still" or "sit idle."