shop assistant vs salesperson

shop assistant and salesperson both are nouns.

Word	Noun	Adjective	Verb	Adverb
shop assistant	Yes	No	No	No
salesperson	Yes	No	No	No

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

shop assistant: a salesperson in a store
salesperson: a person employed to represent a business and to sell its merchandise (as to customers in a store or to customers who are visited)

Other hypernyms of shop assistant include sales rep, sales representative.

shop assistant (noun)	salesperson (noun)
a salesperson in a store	a person employed to represent a business and to sell its merchandise (as to customers in a store or to customers who are visited)