department store vs emporium

department store and emporium both are nouns.

Word	Noun	Adjective	Verb	Adverb
department store	Yes	No	No	No
emporium	Yes	No	No	No

As nouns, department store and emporium are synonyms defined as:

department store and emporium: a large retail store organized into departments offering a variety of merchandise; commonly part of a retail chain

department store (noun)	emporium (noun)
a large retail store organized into departments offering a variety of merchandise; commonly part of a retail chain	a large retail store organized into departments offering a variety of merchandise; commonly part of a retail chain