It is an undoubted substantive proper, and takes a preposition before it, except when it is in the nominative case.
"We Girls: A Home Story"
Mrs. A. D. T. Whitney
The adjective without a substantive is a mere cheat.
"The Memoires of Casanova, Complete The Rare Unabridged London Edition Of 1894, plus An Unpublished Chapter of History, By Arthur Symons"
Jacques Casanova de Seingalt
Now a careful comparison of these and similar passages will make it clear that the sequence presented to us is as follows: The "Word" is the passing of the Verb substantive of Being into Action.
"The Law and the Word"
Thomas Troward