Old Testament vs Song of Solomon

Old Testament and Song of Solomon both are nouns.

Word	Noun	Adjective	Verb	Adverb
Old Testament	Yes	No	No	No
Song of Solomon	Yes	No	No	No

Old Testament (noun)	Song of Solomon (noun)
the collection of books comprising the sacred scripture of the Hebrews and recording their history as the chosen people; the first half of the Christian Bible	an Old Testament book consisting of a collection of love poems traditionally attributed to Solomon but actually written much later