Old Testament vs Book of Ecclesiastes

Old Testament and Book of Ecclesiastes both are nouns.

Word	Noun	Adjective	Verb	Adverb
Old Testament	Yes	No	No	No
Book of Ecclesiastes	Yes	No	No	No

Old Testament (noun)	Book of Ecclesiastes (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 reflections on the vanity of human life; is traditionally attributed to Solomon but probably was written about 250 BC