sorter vs clerk

sorter and clerk both are nouns.

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

As nouns, clerk is a hypernym of sorter; that is, clerk is a word with a broader meaning than sorter:

sorter: a clerk who sorts things (as letters at the post office)
clerk: an employee who performs clerical work (e.g., keeps records or accounts)

sorter (noun)	clerk (noun)
a machine for sorting things (such as punched cards or letters) into classes	an employee who performs clerical work (e.g., keeps records or accounts)
a clerk who sorts things (as letters at the post office)	a salesperson in a store

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