line of merchandise vs business line

line of merchandise and business line both are nouns.

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

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

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

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

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