business line vs line of merchandise

business line and line of merchandise both are nouns.

Word	Noun	Adjective	Verb	Adverb
business line	Yes	No	No	No
line of merchandise	Yes	No	No	No

As nouns, business line and line of merchandise are synonyms defined as:

business line and line of merchandise: a particular kind of product or merchandise

Other synonyms of business line include line, line of business, line of products, product line.

business line (noun)	line of merchandise (noun)
a particular kind of product or merchandise	a particular kind of product or merchandise