shop girl vs clerk

shop girl and clerk both are nouns.

Word	Noun	Adjective	Verb	Adverb
shop girl	Yes	No	No	No
clerk	Yes	No	Yes	No

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

Other hypernyms of shop girl include fille, girl, miss, missy, young lady, young woman, salesclerk, shop assistant, shop clerk.

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

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