shop girl vs salesclerk

shop girl and salesclerk both are nouns.

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

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

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

shop girl (noun)	salesclerk (noun)
a young female shop assistant	a salesperson in a store