The one word that Selden wants to tell Lily is, presumably, the word "love." It is the one word that is conspicuous by its absence throughout the novel — and remains unspoken until the book's final paragraphs. Selden realizes that he still loves Lily, and that their respective differences "had never been more than a little impalpable barrier between them."
Whereas Selden previously would have judged Lily negatively for having a financial transaction with Trenor, Wharton writes that, upon her death, "he felt only a taint of such a transaction." Wharton holds up Selden's cowardice as equally responsible for Lily's downfall and demise as her own actions. Because he feared social reprisal and personal rejection, he abandoned his love for Lily.
