categorise vs class

categorise is not a noun while class is a noun.

Word	Noun	Adjective	Verb	Adverb
categorise	No	No	Yes	No
class	Yes	No	Yes	No

As verbs, class is a hyponym of categorise; that is, class is a word with a more specific, narrower meaning than categorise:

Other hyponyms of categorise include assort, classify, separate, sort, sort out.

categorise (noun)	class (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

categorise (verb)	class (verb)
place into or assign to a category	arrange or order by classes or categories