class vs key out

class is a noun but key out is not a noun.

Word	Noun	Adjective	Verb	Adverb
class	Yes	No	Yes	No
key out	No	No	Yes	No

class (noun)	key out (noun)
education imparted in a series of lessons or meetings
elegance in dress or behavior
a collection of things sharing a common attribute
people having the same social, economic, or educational status
(biology) a taxonomic group containing one or more orders
a body of students who are taught together
a body of students who graduate together
a league ranked by quality

class (verb)	key out (verb)
arrange or order by classes or categories	identify as in botany or biology, for example