Old Testament vs Reuben

Old Testament and Reuben both are nouns.

Word	Noun	Adjective	Verb	Adverb
Old Testament	Yes	No	No	No
Reuben	Yes	No	No	No

Old Testament (noun)	Reuben (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	a hot sandwich with corned beef (or pastrami), Swiss cheese and sauerkraut on rye bread
	(Old Testment) a son of Jacob and forefather of one of the tribes of Israel