Old Testament vs Book of Leviticus

Old Testament and Book of Leviticus both are nouns.

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

Old Testament (noun)	Book of Leviticus (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	the third book of the Old Testament; contains Levitical law and ritual precedents