clerk vs clerical

clerk is a noun but clerical is not a noun.

Word	Noun	Adjective	Verb	Adverb
clerk	Yes	No	Yes	No
clerical	No	Yes	No	No

clerk (noun)	clerical (noun)
an employee who performs clerical work (e.g., keeps records or accounts)
a salesperson in a store

clerk (adjective)	clerical (adjective)
	of or relating to the clergy
	of or relating to clerks
	appropriate for or engaged in office work

clerk (verb)	clerical (verb)
work as a clerk, as in the legal business